Este mạch hở, đơn chức, chứa 50% C (về khối lượng) có tên gọi là? 

A. Vinylaxetat

B. Metylaxetat

C. Etylaxetat

D. Vinylfomat

Cho các chất có công thức cấu tạo sau đây:

    (1) CH₃CH₂COOCH₃;   (2) CH₃OOCCH₃;  

    (3) HCOOC₂H₅;     (4) CH₃COOH;

    (5) CH₃OCOC₂H₃; (6) HOOCCH₂CH₂OH;

(7) CH₃OOCCOOC₂H₅.

Những chất thuộc loại este là

A. (1), (2), (3), (4), (5), (6). 

B. (1), (2), (3), (5), (7). 

C. (1), (2), (4), (6), (7).

D. (1), (2), (3), (6), (7).

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 40 to 47.

Hobbit-like Species of Humans

On the tiny island of Flores, east of Bali and midway between Asia and Australia, the scientists have discovered the remains of a small, hobbit-like species of humans. These people grew no larger than the modern three-year-old child. They lived about 18,000 years ago and are completely different species of human.

This discovery has taught scientists a lot about the human species. This remarkable discovery shows that the human species is more varied and flexible in its ability to adapt than previously thought. These hobbit-like people join a short list of other type of humans that lived with modern humans.

The researchers believe that these hobbits evolved from a normal size, human population that reached Flores around 840,000 years ago. One likely explanation is that, over thousands of years, the species became smaller because the environmental conditions favored a smaller body size. The dwarfing of mammals on islands occurs frequently. Islands limit food supply and predators and species compete for the same environmental space. Survival would depend on minimizing energy requirements.

According to the passage, why does a smaller size help species survive under certain condition?

A. It makes them more difficult for predators to see.

B. It allows them to move more quickly. 

C. It allows them to consume less food.

D. All of the above

chính sách giáo dục, thi cử:

Dựng lại Văn Miếu, mở trường học ở lộ, mọi người đều có thể đi học và đi thi

tuyển chọn người có tài, có đạo đức làm thầy

nho giáo chiếm vị trí độc tôn

mở khoa thi để tuyển chon người tài làm quan

đỗ tiến sĩ được vua ban áo, mủ, tước phẩm, vinh quy bái tổ,khắc tên lên bia đá văn miếu

tuyển chọn công bằng

tác dụng:

cho thấy sự chú trọng của nhà vua với người tài, tuyển chọn một cách công bằng,mọi người đều có quyền đi học, nâng cao kiến thức và ứng tuyển thi cử

chủ động: mẹ cho em tiền

bị động: em được mẹ cho tiền

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 35 to 42.

No sooner had the first intrepid male aviators safely returned to Earth than it seemed that women. too, had been smitten by an urge to fly. From mere spectators, they became willing passengers and finally pilots in their own right, plotting their skills and daring line against the hazards of the air and the skepticism of their male counterparts. In doing so they enlarged the traditional bounds of a women's world, won for their sex a new sense of competence and achievement, and contributed handsomely to the progress of aviation.

But recognition of their abilities did not come easily. "Men do not believe us capable." the famed aviator Amelia Earhart once remarked to a friend. "Because we are women, seldom are we trusted to do an efficient job." Indeed old attitudes died hard: when Charles Lindbergh visited the Soviet Union in i938 with his wife, Anne-herself a pilot and gifted proponent of aviation - he was astonished to discover both men and women flying in the Soviet Air Force.

Such conventional wisdom made it difficult for women to raise money for the up-to-date equipment they needed to compete on an equal basis with men. Yet they did compete, and often they triumphed finally despite the odds.

Ruth Law, whose 590 - mile flight from Chicago to Hornell, New York, set a new nonstop distance record in 1916, exemplified the resourcefulness and grit demanded of any woman who wanted to fly. And when she addressed the Aero Club of America after completing her historic journey, her plain spoken words testified to a universal human motivation that was unaffected by gender: "My flight was done with no expectation of reward," she declared, "just purely for the love of accomplishment."

The word “addressed” can be best replaced by ________.

A. mailed

B. came back to

C. spoke to

D. consulted

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 35 to 42.

No sooner had the first intrepid male aviators safely returned to Earth than it seemed that women. too, had been smitten by an urge to fly. From mere spectators, they became willing passengers and finally pilots in their own right, plotting their skills and daring line against the hazards of the air and the skepticism of their male counterparts. In doing so they enlarged the traditional bounds of a women's world, won for their sex a new sense of competence and achievement, and contributed handsomely to the progress of aviation.

But recognition of their abilities did not come easily. "Men do not believe us capable." the famed aviator Amelia Earhart once remarked to a friend. "Because we are women, seldom are we trusted to do an efficient job." Indeed old attitudes died hard: when Charles Lindbergh visited the Soviet Union in i938 with his wife, Anne-herself a pilot and gifted proponent of aviation - he was astonished to discover both men and women flying in the Soviet Air Force.

Such conventional wisdom made it difficult for women to raise money for the up-to-date equipment they needed to compete on an equal basis with men. Yet they did compete, and often they triumphed finally despite the odds.

Ruth Law, whose 590 - mile flight from Chicago to Hornell, New York, set a new nonstop distance record in 1916, exemplified the resourcefulness and grit demanded of any woman who wanted to fly. And when she addressed the Aero Club of America after completing her historic journey, her plain spoken words testified to a universal human motivation that was unaffected by gender: "My flight was done with no expectation of reward," she declared, "just purely for the love of accomplishment."

What can be inferred from the passage about the United States Air Force in 1938?

A. It had no women pilots

B. It gave pilots handsome salaries

C. It had old planes that were in need of repair

D. It could not be trusted to do an efficient job