Hỗn hợp X gồm etyl axetat, vinyl axetat, glixerol, triaxetat và metyl format. Thủy phân hoàn toàn 20,0 gam X cần dùng vừa đủ 200ml dung dịch NaOH 1,5M. Mặt khác đốt cháy hoàn toàn 20,0 gam X thu được V lit (đktc) CO₂ và 12,6 gam H₂O. Giá trị của V là

A. 14,56 

B. 17,92 

C. 16,80 

D. 22,40 

Read the following passage and mark the letter on your answer sheet to indicate the correct answer

Before photography was invented in 1839, painted portraits, and engravings based on them, were one of the few ways to record likenesses. From the Colonial era through the 1820s, portraiture was the most widely practiced genre of American art, and it continued to be a significant form through the 19th century. The demand for likenesses was incessant, and portraiture was often the primary source of income for artists. Artists frequently made portraits of famous people to attract interest and potential patrons. For example, in 1834 Chester Harding painted frontiersman Davy Crockett, then a member of the U.S. House of Representatives, for display in his Boston gallery.

A consistent belief through most of the 18th and 19th centuries was that character could be read from a person's face, or the bumps on his or her head, or from facial expressions, and that portraits should convey these indicators of character. These theories of physiognomy and phrenology have since been debunked, but they were important considerations in depicting the nation's leaders, since such portraits were often made for posterity. Most people had only one portrait painted in their lifetime, if at all, so artists were selected with great care, and expectations were high.

Before the 1840s, American portraiture was influenced primarily by English techniques, poses, compositions and gestures, and many artists received at least part of their training in England. Even canvas sizes followed the British example. Portraits made on commission were priced according to canvas size and the materials and labor involved.

In the late 19th century as European portraitists began traveling to the United States to acquire commissions from the growing upper class, American artists increasingly felt they needed to train abroad in order to succeed at home. Paris continued to be the main lure. as painters such as Eakins, Whistler, Beaux and Sargent went to study there. Some of America's best-known portraitists, in fact, became expatriates.

In what ways did American artists try to gain greater success? 

A. by inviting European artists to America

B. by traveling abroad 

C. by becoming expatriates

D. by not only painting portraits________

Phần trăm khối lượng của nguyên tố nitơ trong lysin là

A. 17,98%

B. 19,17%

C. 15,73%

D. 19,05%

Dựa vào hình 29.1 (SGK trang 106), hãy nhận xét tỉ lệ diện tích và sản lượng cà phê của Tây Nguyên so với cả nước. Vì sao cây cà phê được trồng nhiều nhất ở vùng này?

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

In The Sociology of Science, _______ a classic, Robert Merton discusses cultural, economic and social forces that contributed to the development of modern science.

A. now considering

B. now considered

C. which considers

D. which considered

Biết mỗi gen quy định 1 tính trạng, các gen phân li độc lập. Phép lai nào sau đây cho tỉ lệ phân li kiểu gen ở đời con là

A. AaBb x aaBb

B. Aabb x aaBb

C. AaBb x AaBb

D. AaBb x aabb