Từ định luật III Kêp-le, hãy suy ra cách tính khối lượng của Mặt Trời theo chu kỳ quay của Trái Đất quanh Mặt Trời.

Các vật phát âm có số liệu như sau âm nào sẽ trầm và to?

A. 50Hz- 100dB

B. 100Hz- 50dB

C. 50Hz- 50dB

D. 100Hz- 100dB

Thực hiện pháp luật không phải là nội dung nào dưới đây?

A. Làm những việc mà pháp luật cấm.

B. Làm những việc mà pháp luật quy định phải làm.

C. Không làm những việc mà pháp luật cấm.

D. Làm những việc mà pháp luật cho phép làm.

Read the following passage and mark the letter A, B, C, D on your answer sheet to indicate the correct answer to each of the questions from 28 to 34.

Stars have been significant features in the design of many United States coins and their number has varied from one to forty-eight stars. Most of the coins issued from about 1799 to the early years of the twentieth century bore thirteen stars representing the thirteen original colonies.

Curiously enough, the first American silver coins, issued in 1794, had fifteen stars because by that time Vermont and Kentucky has joined the Union. At that time it was apparently the intention of mint officials to add a star for each new state. Following the admission of Tennessee in 1796, for example, some varieties of half dimes, dimes, and halfdollars were produced with sixteen stars.

As more states were admitted to the Union, however, it quickly became apparent that this scheme would not prove practical and the coins from A798 on were issued with only thirteen stars-one for each of the original colonies. Due to an error at the mint, one variety of the A828 half cent was issued with only twelve stars. There is also a variety of the large cent with only A2 stars, but this is the result of a die break and is not a true error.

Which of the following is NOT mentioned as the denomination of an American coin?

A. Half cent

B. Half-dollar

C. Half dime

D. Half nickel 

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 molecule 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.

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

He wanted to know whose car I borrowed _____.

A. Yesterday

B. the last evening

C. last night

D. the previous night 

Dãy gồm các chất đều tác dụng với H₂ (xúc tác Ni, t°), tạo ra sản phẩm thu được có khả năng phản ứng với Na là

A. CH₃OC₂H₅, CH₃CHO, C₂H₃COOH.

B. C₂H₃CH₂OH, CH₃COCH₃, C₂H₃COOH.

C. C₂H₃CH₂OH, CH₃CHO, CH₃COOH.

D. C₂H₃CHO, CH₃COOC₂H₃, C₆H₅COOH.

Trong quá trình tổng hợp ARN không xảy ra hiện tượng nào sau đây?

A. X trên mạch gốc liên kết với G của môi trường.

B. G mạch gốc liên kết với X của môi trường nội bào.

C. A trên mạch gốc liên kết với T của môi trường.

D. T trên mạch gốc liên kết với A của môi trường.