yêu cầu dẫn chứng nữa nhé 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 from 43 to 50. Carbon dating can be used to estimate the age of any organic natural material; it has been used successfully in archeology to determine the age of ancient artifacts or fossils as well as in a variety of other fields. The principle underlying the use of carbon dating is that carbon is a part of all living things on Earth. Since a radioactive substance such as carbon-14 has a known half- life, the amount of carbon-14 remaining in an object can be used to date that object. Carbon-14 has a half-life of 5,570 years, which means that after that number of years, half of the carbon- 14 atoms have decayed into nitrogen-14. It is the ratio of carbon-14 in that substance that indicates the age of the substance. If, for example, in a particular sample the amount of carbon-14 is roughly equivalent to the amount of nitrogen-14, this indicates that around half of the carbon-14 has decayed into nitrogen-14, and the sample is approximately 5,570 years old. Carbon dating cannot be used effectively in dating objects that are older than 80,000 years. When objects are that old, much of the carbon-14 has already decayed into nitrogen-14, and the miniscule amount that is left doesn’t provide a reliable measurement of age. In the case of older objects, other age- dating methods are available, methods which use radioactive atoms with longer half-lives than carbon has. Question 41: This passage is mainly about . A. archeology and the study of ancient artifacts B. one method of dating old objects C. various uses for carbon D. the differences between carbon-14 and nitrogen-14 Question 42: Which of the following is NOT true about carbon-14? A. It and nitrogen always exist in equal amounts in any substance. B. Its half-life is more than 5,000 years. C. It can decay into nitrogen-14. D. It is radioactive. Question 43: The word “it” in paragraph I refers to . A. carbon dating B. the age C. any organic natural material D. archeology Question 44: The word “underlying” in paragraph I could best be replaced by . A. below B. requiring C. serving as a basis for D. being studied through Question 45: The word “roughly” in paragraph 2 is closest in meaning to . A. precisely B. harshly C. approximately D. coarsely Question 46: The paragraph following the passage most probably discusses . A. what substances are part of all living things B. how carbon-14 decay intonitrogen-14 C. why carbon-14 has such a long half-life D. various other age-dating methods Question 47: It is implied in the passage that . A. carbon dating has no known uses outside of archeology B. fossils cannot be age-dated using carbon-14 C. carbon dating could not be used on an item containing nitrogen D. carbon-14 does not have the longest known half-life Question 48: It can be inferred from the passage that if an item contains more carbon-14 than nitrogen- 14, then the item is . A. not as much as 5,570 years old B. too old to be age-dated with carbon-14 C. too radioactive to be used by archeologists D. more than 5.570 years old Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best completes each of the following exchanges. Question 49: Two friends, Diana and Anne, are talking about Anne’s new blouse. Diana: “That blouse suits you perfectly, Anne.” Anne: “ .” A. Never mind B. Don’t mention it C. Thank you D. You’re welcome Question 50: Mary is talking to a porter in the hotel lobby. Porter: “Shall I help you with your suitcase?” Mary: “ ” A. Not a chance. B. That’s very kind of you. C. I can‘t agree more. D. What a pity!

Question 41: This passage is mainly about

B. one method of dating old objects 

Câu đầu, thứ 2, hay cuối của đoạn văn thường nêu ý chính. Trong trường hợp này, ngay câu đầu "Carbon dating can be used to estimate the age of any organic natural material" đã chỉ rõ đoạn này viết về cách tính tuổi bất kỳ vật liệu hữu cơ tự nhiên nào bằng carbon.

Question 42: Which of the following is NOT true about carbon-14?

A. It and nitrogen always exist in equal amounts in any substance.

Có thể dùng phép loại trừ vì các tính chất nêu trong câu B, C, D đều có trong 2 câu

Since a radioactive substance such as carbon-14 has a known half- life, the amount of carbon-14 remaining in an object can be used to date that object. Carbon-14 has a half-life of 5,570 years, which means that after that number of years, half of the carbon- 14 atoms have decayed into nitrogen-14.

Để chắc chắn câu A sai, có thể xem tiếp:

It is the ratio of carbon-14 in that substance that indicates the age of the substance. If, for example, in a particular sample the amount of carbon-14 is roughly equivalent to the amount of nitrogen-14, this indicates that around half of the carbon-14 has decayed into nitrogen-14, and the sample is approximately 5,570 years old.

Cái ví dụ nêu ra cách tính tuổi vật mẫu (sample) khi lượng carbon-14 bằng nitrogen-14, tức là không phải lúc nào lượng 2 chât này cũng bằng nhau vì tuổi đồ vật thay đổi theo thời gian.

Question 43: The word “it” in paragraph I refers to

A. carbon dating

Carbon dating can be used to estimate the age of any organic natural material; it has been used successfully in archeology to determine the age of ancient artifacts or fossils as well as in a variety of other fields.

Question 44: The word “underlying” in paragraph I could best be replaced by

C. serving as a basis for

Question 45: The word “roughly” in paragraph 2 is closest in meaning to

C. approximately 

Question 46: The paragraph following the passage most probably discusses

D. various other age-dating methods

Câu cuối

In the case of older objects, other age- dating methods are available, methods which use radioactive atoms with longer half-lives than carbon has.

Question 47: It is implied in the passage that

D. carbon-14 does not have the longest known half-life

In the case of older objects, other age- dating methods are available, methods which use radioactive atoms with longer half-lives than carbon has.

Các câu sai: 

A. carbon dating has no known uses outside of archeology

[Carbon dating] has been used successfully in archeology to determine the age of ancient artifacts or fossils as well as in a variety of other fields

B. fossils cannot be age-dated using carbon-14

[Carbon dating] has been used successfully in archeology to determine the age of ancient artifacts or fossils as well as in a variety of other fields

C. carbon dating could not be used on an item containing nitrogen

Không có nhắc đến trong văn bản

Question 48: It can be inferred from the passage that if an item contains more carbon-14 than nitrogen- 14, then the item is

A. not as much as 5,570 years old

Carbon-14 has a half-life of 5,570 years, which means that after that number of years, half of the carbon- 14 atoms have decayed into nitrogen-14

Vì Carbon-14 sẽ dần chuyển thành Nitrogen-14 theo thời gian cho đến khi lượng Carbon 14 bằng lượng Nitrogen-14 thì đã trôi qua 5570 năm

If, for example, in a particular sample the amount of carbon-14 is roughly equivalent to the amount of nitrogen-14, this indicates that around half of the carbon-14 has decayed into nitrogen-14, and the sample is approximately 5,570 years old.

Vậy khi lượng Carbon-14 còn nhiều hơn lượng Nitrogen-14 thì chưa qua hết 5570 năm.

Question 49: Two friends, Diana and Anne, are talking about Anne’s new blouse.

Diana: “That blouse suits you perfectly, Anne.”

Anne: “ .”

C. Thank you

Khi được khen thì cách trả lời cơ bản nhất là cảm ơn

Question 50: Mary is talking to a porter in the hotel lobby.

Porter: “Shall I help you with your suitcase?”

Mary: “ ”

B. That’s very kind of you. 

"That's very kind of you" là cách trả lời lịch sự khi tiếp nhận đề nghị giúp đỡ từ người khác. Có thể dịch là "Bạn thật tử tế"