Trong trường hợp một gen qui định một tính trạng, gen trội là trội hoàn toàn, các gen phân li độc lập, tổ hợp tự do. Phép lai AaBb × aabb cho đời con có sự phân li kiểu hình theo tỉ lệ

A.   1:1:1:1

B. 3:1

C. 9:3:3:1

D. 1:1

Hai chất CH 3 COOH và CH2=CH-COOH giống nhau về ?

A. Công thức phân tử.

B. Công thức cấu tạo.

C. Loại nhóm chức.

D. Loại liên kết hóa học .

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.

Herman Melville, an American author best known today for his novel Moby Dick, was actually more popular during his lifetime for some of his other works. He traveled extensively and used the knowledge gained during his travels as the basis for his early novels. In 1837, at the age of eighteen, Melville signed as a cabin boy on a merchant ship that was to sail from his Massachusetts home to Liverpool, England. His experiences on this trip served as a basis for the novel Redburn (1849). In 1841 Melville set out on a whaling ship headed for the South Seas. After jumping ship in Tahiti, he wandered around the islands of Tahiti and Moorea. This South Sea island sojourn was a backdrop to the novel Omoo (1847). After three years away from home, Melville joined up with a U.S. naval frigate that was returning to the eastern United States around Cape Horn. The novel White-Jacket (1850) describes this lengthy voyage as a navy seaman. With the publication of these early adventure novels, Melville developed a strong and loyal following among readers eager for his tales of exotic places and situations. However, in 1851, with the publication of Moby Dick, Melville's popularity started to diminish. Moby Dick, on one level the saga of the hunt for the great white whale, was also a heavily symbolic allegory of the heroic struggle of man against the universe. The public was not ready for Melville's literary metamorphosis from romantic adventure to philosophical symbolism. It is ironic that the novel that served to diminish Melville's popularity during his lifetime is the one for which he is best known today.

In what year did Melville’s book about his experiences as a cabin boy appear?

A. 1849

B. 1837

C. 1847

D. 1841

Mark the letter A, B, C, or D on your answer sheet to indicate the word(s) CLOSEST in meaning to the underlined word(s) in each of the following questions.

In the twentieth century, drug markedly improved health throughout the world.

A. consistently

B. supposedly

C. noticeably

D. recently