Water is made up of two elements.They are __________ .A.Nitrogen and Hydrogen B.Oxygen and NitrogenC.Hydrogen and Oxygen D.Nitrogen and Helium

KS

Kochou Shinobu

15 tháng 7 2021 - olm

Water is made up of two elements.They are __________ .

A.Nitrogen and Hydrogen

B.Oxygen and Nitrogen

C.Hydrogen and Oxygen

D.Nitrogen and Helium

#Tiếng anh lớp 5

2

DA

Đặng Anh Thư

15 tháng 7 2021

C.Hydrogen and Oxygen

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PA

Phan Anh Minh(*•.¸♡ţęąɱ ƒŗęę ƒįŗę❤☆...

15 tháng 7 2021

dap an

C

hok tot

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VP

Vũ Phương Thao

24 tháng 3 2021 - olm

Read the text and answer the following questions. SATURN Saturn is the second-largest planet and is a gas giant like Jupiter. Under clouds of methane, hydrogen, and helium, the sky slowly turns into a giant ocean of liquid chemicals. Saturn is the least dense planet in our solar system; it is made mostly of hydrogen and helium. Because it is so lightweight and spins so quickly, Saturn is not perfectly round like the other planets. Saturn is surrounded by thousands of small rings made of...

Đọc tiếp

#Tiếng anh lớp 9

15

LD

l҉o҉n҉g҉ d҉z҉

24 tháng 3 2021

1. It is a gas giant Jupiter.

2. Clouds are made of methane, hydrogen, and helium.

3. Saturn is the least dense planet in our solar system and is made mostly of hydrogen and helium.

4. Because it is so lightweight and spins so quickly.

5. Saturn is surrounded by thousands of small rings made of rocks and rice.

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NT

Nguyễn Tuấn Hưng

31 tháng 12 2021

1 It is a gas giant like Jupiter.

2 Clouds are made of methane, hydrogen, and helium.

3 Saturn is the least dense planet in our solar system and is made mostly of hydrogen and helium.

4 Because it is so lightweight and spins so quickly.

5 Saturn is surrounded by thousands of small rings made of rocks and rice.

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LQ

Lê Quỳnh Anh

29 tháng 11 2017

Mark the letter A, B, c, or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions.

Sugars (A) like glucose (B) is (C) made (D) up of carbon, hydrogen, and oxygen atoms.

#Mẫu giáo

1

DH

Dương Hoàn Anh

29 tháng 11 2017

Chọn B

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LQ

Lê Quỳnh Anh

4 tháng 6 2017

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions. The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 25 percent helium by weight and somewhat less than 75 percent hydrogen. Astronomers have measured the abundance of helium throughout our galaxy and in other galaxies as well. Helium has been found in old stars, in...

Đọc tiếp

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions.

The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 25 percent helium by weight and somewhat less than 75 percent hydrogen.

Astronomers have measured the abundance of helium throughout our galaxy and in other galaxies as well. Helium has been found in old stars, in relatively young ones, in interstellar gas, and in the distant objects known as quasars. Helium nuclei have also been found to be constituents of cosmic rays that fall on the earth (cosmic rays are not really a form of radiation; they consist of rapidly moving particles of numerous different kinds). It doesn’t seem to make very much difference where the helium is found. Its relative abundance never seems to vary much. In some places, there may be slightly more of it; in others, slightly less, but the ratio of helium to hydrogen nuclei always remains about the same.

Helium is created in stars. In fact, nuclear reactions that convert hydrogen to helium are responsible for most of the energy that stars produce. However, the amount of helium that could have been produced in this manner can be calculated, and it turns out to be no more than a few percent. The universe has not existed long enough for this figure to be significant greater. Consequently, if the universe is somewhat more than 25 percent helium now, then it must have been about 25 percent helium at a time near the beginning.

However, when the universe was less than one minute old, no helium could have existed. Calculations indicate that before this time temperature were too high and particles of matter were moving around much too rapidly. It was only after the one-minute point that helium could exist. By this time, the universe had cooled so sufficiently that neutrons and protons could stick together. But the nuclear reactions that led to the formations of helium went on for only relatively short time. By the time the universe was a few minutes old, helium production had effectively ceased.

According to the passage, helium is ________

A. the most prevalent element in quasars

B. difficult to detect

C. the oldest element in the universe

D. the second-most abundant element in the universe

#Mẫu giáo

1

DH

Dương Hoàn Anh

4 tháng 6 2017

Kiến thức: Đọc hiểu

Giải thích:

Theo đoạn văn, khí heli là ________

A. nguyên tố phổ biến nhất trong chuẩn tinh B. khó để phát hiện

C. nguyên tố lâu đời nhất trong vũ trụ D. nguyên tố phong phú thứ hai trong vũ trụ

Thông tin: The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 25 percent helium by weight and somewhat less than 75 percent hydrogen.

Tạm dịch: Các yếu tố ngoài Hydro và Heli tồn tại với số lượng nhỏ đến nỗi chính xác khi nói rằng theo trọng lượng, vũ trụ có phần hơn 25 phần trăm heli tính và phần nào ít hơn 75 phần trăm Hydro.

Chọn D

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LQ

Lê Quỳnh Anh

8 tháng 4 2019

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions. The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 25 percent helium by weight and somewhat less than 75 percent hydrogen. Astronomers have measured the abundance of helium throughout our galaxy and in other galaxies as well. Helium has been found in old stars, in...

Đọc tiếp

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions.

The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 25 percent helium by weight and somewhat less than 75 percent hydrogen.

Astronomers have measured the abundance of helium throughout our galaxy and in other galaxies as well. Helium has been found in old stars, in relatively young ones, in interstellar gas, and in the distant objects known as quasars. Helium nuclei have also been found to be constituents of cosmic rays that fall on the earth (cosmic rays are not really a form of radiation; they consist of rapidly moving particles of numerous different kinds). It doesn’t seem to make very much difference where the helium is found. Its relative abundance never seems to vary much. In some places, there may be slightly more of it; in others, slightly less, but the ratio of helium to hydrogen nuclei always remains about the same.

Helium is created in stars. In fact, nuclear reactions that convert hydrogen to helium are responsible for most of the energy that stars produce. However, the amount of helium that could have been produced in this manner can be calculated, and it turns out to be no more than a few percent. The universe has not existed long enough for this figure to be significant greater. Consequently, if the universe is somewhat more than 25 percent helium now, then it must have been about 25 percent helium at a time near the beginning.

However, when the universe was less than one minute old, no helium could have existed. Calculations indicate that before this time temperature were too high and particles of matter were moving around much too rapidly. It was only after the one-minute point that helium could exist. By this time, the universe had cooled so sufficiently that neutrons and protons could stick together. But the nuclear reactions that led to the formations of helium went on for only relatively short time. By the time the universe was a few minutes old, helium production had effectively ceased.

Most of the helium in the universe was formed ______

A. during the first minute of the universe's existence

B. in a very short time

C. in interstellar space

D. before most of the hydrogen

#Mẫu giáo

1

DH

Dương Hoàn Anh

8 tháng 4 2019

Kiến thức: Đọc hiểu

Giải thích:

Hầu hết helium trong vũ trụ được hình thành ______

A. trong phút đầu tiên của sự tồn tại của vũ trụ B. trong một thời gian rất ngắn

C. trong không gian giữa các vì sao D. trước phần lớn hydro

Thông tin: However, when the universe was less than one minute old, no helium could have existed. Calculations indicate that before this time temperature were too high and particles of matter were moving around much too rapidly. It was only after the one-minute point that helium could exist.

Tạm dịch: Tuy nhiên, khi vũ trụ hình thành chưa đầy một phút, Heli đã không thể tồn tại. Các tính toán cho thấy rằng trước khi nhiệt độ thời gian này là quá cao và các hạt của vật chất đã được di chuyển xung quanh nhiều quá nhanh. Chỉ sau mốc một phút Heli mới thể tồn tại.

Chọn B

Dịch bài đọc:

Các yếu tố ngoài Hydro và Heli tồn tại với số lượng nhỏ đến nỗi chính xác khi nói rằng theo trọng lượng, vũ trụ có phần hơn 25 phần trăm heli tính và phần nào ít hơn 75 phần trăm Hydro.

Các nhà thiên văn đã đo sự dư thừa của Heli khắp thiên hà của chúng ta và các thiên hà khác. Heli đã được tìm thấy trong những ngôi sao tồn tại đã lâu, ở những ngôi sao tương đối mới, trong khí giữa các vì sao, và trong các đối tượng ở xa gọi là chuẩn tinh. Hạt nhân helium cũng đã được tìm thấy là thành phần của các tia vũ trụ chiếu xuống Trái đất (tia vũ trụ không phải là thực sự là một dạng bức xạ, chúng gồm các hạt của nhiều loại khác nhau di chuyển nhanh chóng). Nó dường như không làm khác biệt đi nhiều nơi Heli được tìm thấy. Sự phong phú tương đối của nó dường như không bao giờ thay đổi nhiều. Ở một số nơi, có thể có nhiều hơn một chút; ở những nơi khác, một chút ít, nhưng tỷ lệ Heli trên các hạt nhân Hydro luôn luôn vẫn như nhau.

Helium được tạo ra trong các ngôi sao. Trong thực tế, phản ứng hạt nhân mà chuyển đổi Hydro thành Heli đảm nhiệm hầu hết năng lượng mà các ngôi sao tạo ra. Tuy nhiên, lượng Heli có thể đã được sản xuất theo cách này có thể được tính toán, và hóa ra là không có nhiều hơn một vài phần trăm. Vũ trụ đã không tồn tại đủ lâu để con số này là lớn hơn đáng kể. Do đó, nếu vũ trụ là có phần hơn 25 % Heli bây giờ, thì nó phải có được khoảng 25% Heli tại một thời điểm gần lúc nó hình thành.

Tuy nhiên, khi vũ trụ hình thành chưa đầy một phút, Heli đã không thể tồn tại. Các tính toán cho thấy rằng trước khi nhiệt độ thời gian này là quá cao và các hạt của vật chất đã được di chuyển xung quanh nhiều quá nhanh. Chỉ sau mốc một phút Heli mới thể tồn tại. Đến thời điểm này, vũ trụ đã quá nguội đến nỗi Nơtron và Proton có thể kết hợp vào nhau. Nhưng phản ứng hạt nhân dẫn đến sự hình thành của Heli đã hoàn thiện trong một thời gian tương đối ngắn. Sau khi vũ trụ được hình thành vài phút, việc tạo ra Heli đã không còn hiệu quả.

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LQ

Lê Quỳnh Anh

23 tháng 1 2017

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions. The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 25 percent helium by weight and somewhat less than 75 percent hydrogen. Astronomers have measured the abundance of helium throughout our galaxy and in other galaxies as well. Helium has been found in old stars, in...

Đọc tiếp

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions.

The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 25 percent helium by weight and somewhat less than 75 percent hydrogen.

Astronomers have measured the abundance of helium throughout our galaxy and in other galaxies as well. Helium has been found in old stars, in relatively young ones, in interstellar gas, and in the distant objects known as quasars. Helium nuclei have also been found to be constituents of cosmic rays that fall on the earth (cosmic rays are not really a form of radiation; they consist of rapidly moving particles of numerous different kinds). It doesn’t seem to make very much difference where the helium is found. Its relative abundance never seems to vary much. In some places, there may be slightly more of it; in others, slightly less, but the ratio of helium to hydrogen nuclei always remains about the same.

Helium is created in stars. In fact, nuclear reactions that convert hydrogen to helium are responsible for most of the energy that stars produce. However, the amount of helium that could have been produced in this manner can be calculated, and it turns out to be no more than a few percent. The universe has not existed long enough for this figure to be significant greater. Consequently, if the universe is somewhat more than 25 percent helium now, then it must have been about 25 percent helium at a time near the beginning.

However, when the universe was less than one minute old, no helium could have existed. Calculations indicate that before this time temperature were too high and particles of matter were moving around much too rapidly. It was only after the one-minute point that helium could exist. By this time, the universe had cooled so sufficiently that neutrons and protons could stick together. But the nuclear reactions that led to the formations of helium went on for only relatively short time. By the time the universe was a few minutes old, helium production had effectively ceased.

The creation of helium within stars ______

A. produces hydrogen as a by-product

B. causes helium to be much more abundant in old stars than in young st

C. produces energy

D. cannot be measured

#Mẫu giáo

1

DH

Dương Hoàn Anh

23 tháng 1 2017

Kiến thức: Đọc hiểu

Giải thích:

Việc tạo ra helium trong các ngôi sao ______

A. sản xuất hydro dưới dạng sản phẩm phụ B. làm cho helium có nhiều ở các ngôi sao tồn tại đã lâu hơn nhiều so với sao mới được hình thành

C. tạo ra năng lượng D. không thể đo được

Thông tin: Helium is created in stars. In fact, nuclear reactions that convert hydrogen to helium are responsible for most of the energy that stars produce.

Tạm dịch: Helium được tạo ra trong các ngôi sao. Trong thực tế, phản ứng hạt nhân mà chuyển đổi Hydro thành Heli đảm nhiệm hầu hết năng lượng mà các ngôi sao tạo ra.

Chọn C

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LQ

Lê Quỳnh Anh

27 tháng 8 2019

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions. The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 25 percent helium by weight and somewhat less than 75 percent hydrogen. Astronomers have measured the abundance of helium throughout our galaxy and in other galaxies as well. Helium has been found in old stars, in...

Đọc tiếp

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions.

The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 25 percent helium by weight and somewhat less than 75 percent hydrogen.

Astronomers have measured the abundance of helium throughout our galaxy and in other galaxies as well. Helium has been found in old stars, in relatively young ones, in interstellar gas, and in the distant objects known as quasars. Helium nuclei have also been found to be constituents of cosmic rays that fall on the earth (cosmic rays are not really a form of radiation; they consist of rapidly moving particles of numerous different kinds). It doesn’t seem to make very much difference where the helium is found. Its relative abundance never seems to vary much. In some places, there may be slightly more of it; in others, slightly less, but the ratio of helium to hydrogen nuclei always remains about the same.

Helium is created in stars. In fact, nuclear reactions that convert hydrogen to helium are responsible for most of the energy that stars produce. However, the amount of helium that could have been produced in this manner can be calculated, and it turns out to be no more than a few percent. The universe has not existed long enough for this figure to be significant greater. Consequently, if the universe is somewhat more than 25 percent helium now, then it must have been about 25 percent helium at a time near the beginning.

However, when the universe was less than one minute old, no helium could have existed. Calculations indicate that before this time temperature were too high and particles of matter were moving around much too rapidly. It was only after the one-minute point that helium could exist. By this time, the universe had cooled so sufficiently that neutrons and protons could stick together. But the nuclear reactions that led to the formations of helium went on for only relatively short time. By the time the universe was a few minutes old, helium production had effectively ceased.

The word "constituents" is closest in meaning to _____

A. causes

B. components

C. relatives

D. targets

#Mẫu giáo

1

DH

Dương Hoàn Anh

27 tháng 8 2019

Kiến thức: Đọc hiểu, từ vựng

Giải thích:

constituent (n): thành phần

cause (n): nguyên nhân component (n): thành phần

relative (n): họ hàng target (n): mục tiêu

=> constituent = component

Thông tin: Helium nuclei have also been found to be constituents of cosmic rays that fall on the earth

Tạm dịch: Hạt nhân helium cũng đã được tìm thấy là thành phần của các tia vũ trụ chiếu xuống Trái đất

Chọn B

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LQ

Lê Quỳnh Anh

1 tháng 9 2017

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions. The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 25 percent helium by weight and somewhat less than 75 percent hydrogen. Astronomers have measured the abundance of helium throughout our galaxy and in other galaxies as well. Helium has been found in old stars, in...

Đọc tiếp

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions.

The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 25 percent helium by weight and somewhat less than 75 percent hydrogen.

Astronomers have measured the abundance of helium throughout our galaxy and in other galaxies as well. Helium has been found in old stars, in relatively young ones, in interstellar gas, and in the distant objects known as quasars. Helium nuclei have also been found to be constituents of cosmic rays that fall on the earth (cosmic rays are not really a form of radiation; they consist of rapidly moving particles of numerous different kinds). It doesn’t seem to make very much difference where the helium is found. Its relative abundance never seems to vary much. In some places, there may be slightly more of it; in others, slightly less, but the ratio of helium to hydrogen nuclei always remains about the same.

Helium is created in stars. In fact, nuclear reactions that convert hydrogen to helium are responsible for most of the energy that stars produce. However, the amount of helium that could have been produced in this manner can be calculated, and it turns out to be no more than a few percent. The universe has not existed long enough for this figure to be significant greater. Consequently, if the universe is somewhat more than 25 percent helium now, then it must have been about 25 percent helium at a time near the beginning.

However, when the universe was less than one minute old, no helium could have existed. Calculations indicate that before this time temperature were too high and particles of matter were moving around much too rapidly. It was only after the one-minute point that helium could exist. By this time, the universe had cooled so sufficiently that neutrons and protons could stick together. But the nuclear reactions that led to the formations of helium went on for only relatively short time. By the time the universe was a few minutes old, helium production had effectively ceased.

The word "vary" is closest in meaning to

A. include

B. mean

C. stretch

D. change

#Mẫu giáo

1

DH

Dương Hoàn Anh

1 tháng 9 2017

Kiến thức: Đọc hiểu, từ vựng

Giải thích:

vary (v): thay đổi

include (v): bao gồm mean (v): có nghĩa là

stretch (v): căng ra change (v): thay đổi

=> vary = change

Thông tin: Its relative abundance never seems to vary much.

Tạm dịch: Sự phong phú tương đối của nó dường như không bao giờ thay đổi nhiều.

Chọn D

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LQ

Lê Quỳnh Anh

9 tháng 12 2018

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions. As a result of pollution, Lake Erie, on the borders of the USA and Canada, is now without any living things. Pollutions in water are not simply a matter of “poisons” killing large numbers of fish overnight. Very often the effects of pollution are not noticed for many months or years because the first organisms to be affected are either plants or...

Đọc tiếp

#Mẫu giáo

1

DH

Dương Hoàn Anh

9 tháng 12 2018

Đáp án D

Ô nhiễm chỉ được chú ý tới ______.
A. khi sinh vật đầu tiên bị ảnh hưởng.
B. ngay sau khi sự cân bằng tự nhiên bị phá hủy.
C. khi chất độc bị đổ xuống nguồn nước.
D. khi nhiều loài cá và chim bị chết.
Dẫn chứng câu 3-5 đoạn 1: “Very often the effects of pollution are not noticed for many months or years because the first organisms to be affected are either plants or plankton. But these organisms are the food of fish and birds and other creatures. When this food disappears, the fish and birds die in this way a whole food chain can be wiped out, and it is not until dead fish and water birds are seen at the river’s edge or on the sea shore that people realize what is happening” – (Những tác động thường xuyên của ô nhiễm không được chú ý tới trong vài tháng, thậm chí là vài năm bởi sinh vật đầu tiên bị ảnh hưởng chỉ là các loài thực vật hoặc các sinh vật phù du. Nhưng đối với những sinh vật làm thức ăn cho cá, chim hoặc và loài sinh vật khác. Khi chúng biến mất thì cá, chim cũng chết theo như cách mà 1 chuỗi thức ăn bị xóa sổ, và cho đến khi xác chết chim, cá được nhìn thấy trên mặt hồ hoặc bờ biển thì con người mới nhận thức được rằng điều gì đang xảy ra).

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LQ

Lê Quỳnh Anh

25 tháng 11 2017

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions. The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 25 percent helium by weight and somewhat less than 75 percent hydrogen. Astronomers have measured the abundance of helium throughout our galaxy and in other galaxies as well. Helium has been found in old stars, in...

Đọc tiếp

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions.

The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 25 percent helium by weight and somewhat less than 75 percent hydrogen.

Astronomers have measured the abundance of helium throughout our galaxy and in other galaxies as well. Helium has been found in old stars, in relatively young ones, in interstellar gas, and in the distant objects known as quasars. Helium nuclei have also been found to be constituents of cosmic rays that fall on the earth (cosmic rays are not really a form of radiation; they consist of rapidly moving particles of numerous different kinds). It doesn’t seem to make very much difference where the helium is found. Its relative abundance never seems to vary much. In some places, there may be slightly more of it; in others, slightly less, but the ratio of helium to hydrogen nuclei always remains about the same.

Helium is created in stars. In fact, nuclear reactions that convert hydrogen to helium are responsible for most of the energy that stars produce. However, the amount of helium that could have been produced in this manner can be calculated, and it turns out to be no more than a few percent. The universe has not existed long enough for this figure to be significant greater. Consequently, if the universe is somewhat more than 25 percent helium now, then it must have been about 25 percent helium at a time near the beginning.

However, when the universe was less than one minute old, no helium could have existed. Calculations indicate that before this time temperature were too high and particles of matter were moving around much too rapidly. It was only after the one-minute point that helium could exist. By this time, the universe had cooled so sufficiently that neutrons and protons could stick together. But the nuclear reactions that led to the formations of helium went on for only relatively short time. By the time the universe was a few minutes old, helium production had effectively ceased.

The word "they" refers to _____

A. particles

B. cosmic rays

C. constituents

D. radiation

#Mẫu giáo

1

DH

Dương Hoàn Anh

25 tháng 11 2017

Kiến thức: Đọc hiểu

Giải thích:

Từ "they" dùng để chỉ _____

A. hạt B. tia vũ trụ

C. thành phần D. bức xạ

Thông tin: cosmic rays are not really a form of radiation; they consist of rapidly moving particles of numerous different kinds

Tạm dịch: tia vũ trụ không phải là thực sự là một dạng bức xạ, chúng gồm các hạt của nhiều loại khác nhau di chuyển nhanh chóng

Chọn B

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LQ

Lê Quỳnh Anh

20 tháng 1 2019

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions. The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 25 percent helium by weight and somewhat less than 75 percent hydrogen. Astronomers have measured the abundance of helium throughout our galaxy and in other galaxies as well. Helium has been found in old stars, in...

Đọc tiếp

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions.

The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 25 percent helium by weight and somewhat less than 75 percent hydrogen.

Astronomers have measured the abundance of helium throughout our galaxy and in other galaxies as well. Helium has been found in old stars, in relatively young ones, in interstellar gas, and in the distant objects known as quasars. Helium nuclei have also been found to be constituents of cosmic rays that fall on the earth (cosmic rays are not really a form of radiation; they consist of rapidly moving particles of numerous different kinds). It doesn’t seem to make very much difference where the helium is found. Its relative abundance never seems to vary much. In some places, there may be slightly more of it; in others, slightly less, but the ratio of helium to hydrogen nuclei always remains about the same.

Helium is created in stars. In fact, nuclear reactions that convert hydrogen to helium are responsible for most of the energy that stars produce. However, the amount of helium that could have been produced in this manner can be calculated, and it turns out to be no more than a few percent. The universe has not existed long enough for this figure to be significant greater. Consequently, if the universe is somewhat more than 25 percent helium now, then it must have been about 25 percent helium at a time near the beginning.

However, when the universe was less than one minute old, no helium could have existed. Calculations indicate that before this time temperature were too high and particles of matter were moving around much too rapidly. It was only after the one-minute point that helium could exist. By this time, the universe had cooled so sufficiently that neutrons and protons could stick together. But the nuclear reactions that led to the formations of helium went on for only relatively short time. By the time the universe was a few minutes old, helium production had effectively ceased.

Why does the author mention "cosmic rays"?

A. To explain the abundance of hydrogen in the universe

B. To explain how the universe began

C. As an example of an unsolved astronomical puzzle

D. As part of a list of things containing helium

#Mẫu giáo

1

DH

Dương Hoàn Anh

20 tháng 1 2019

Kiến thức: Đọc hiểu

Giải thích:

Tại sao tác giả đề cập đến “các tia vũ trụ”?

A. Để giải thích sự phong phú của hydro trong vũ trụ B. Để giải thích về việc vũ trụ bắt đầu như thế nào

C. Để lấy ví dụ về câu đố về thiên văn chưa giải quyết D. Nó là một phần của danh sách những thứ có chứa khí heli

Thông tin: Helium nuclei have also been found to be constituents of cosmic rays that fall on the earth

Tạm dịch: Hạt nhân helium cũng đã được tìm thấy là thành phần của các tia vũ trụ chiếu xuống Trái đất

Chọn D

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