Thủy phân hoàn toàn một tripeptit (mạch hở) thu được hỗn hợp gồm alanin và glyxin theo tỷ lệ mol là 2 : 1. Số tripeptit thỏa mãn là: 

A. 1. 

B. 3. 

C. 2. 

D. 4. 

Có các kết luận sau:

(a) Từ glyxin, alanin và valin sẽ tạo ra được 6 tripeptit chứa đồng thời glyxin, alanin và valin.

(b) C 8 H 10 O có 4 ancol thơm khi bị oxi hóa bởi CuO tạo ra sản phẩm có khả năng tham gia phản ứng tráng gương.

(c) C 4 H 8  có 4 đồng phân mạch hở làm mất màu dung dịch brom.

(d) C 4 H 11 N có 4 đồng phân khi tác dụng với HCl tạo ra muối dạng RNH 3 Cl .

Số kết luận đúng là

A. 2

B. 4

C. 3

D. 1

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

Who talk more – men or women? Most people believe that women talk more. However, linguist Deborah Tannen, who has studied the communication style of men and women, says that this is a stereotype. According to Tannen, women are more verbal – talk more – in private situations, where they use conversation as the “glue” to hold relationships together. But, she says, men talk more in public situations, where they use conversation to exchange information and gain status. Tannen points out that we can see these differences even in children. Little girls often play with one “best friend”, their play includes a lot of conversation. Little boys often play games in groups; their play usually involves more doing than talking. In school, girls are often better at verbal skills, boys are often better at mathematics.

A recent study at Emory University helps to shed light on the roots of this difference. Researchers studied conversation between children age 3-6 and their parents. They found evidence that parents talk very differently to their son than they do to their daughters. The startling conclusion was that parents use more language with their girls. Specifically, when parents talk with their daughters, they use more descriptive language and more details. There is also far more talk about emotions, especially sadness, with daughters than with sons.

Which  word is similar in meaning to  “glue”  in line 5 ?

A. means              

B. sticky substance                  

C. game                

D. rope