Cho dãy các chất: (1) metyl fomat, (2) glucozơ, (3) fructozơ, (4) axit fomic, (5) saccarozơ. Số chất có khả năng tham gia phản ứng tráng bạc là 

A. 2

B. 3

C. 4

D. 5

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions
Mr. Nixon refused to answer the questions on the________that the matter was confidential.

A. reasons

B. excuses

C. grounds

D. foundation

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

The boy insisted on ___________ a break after lunch.

A. having

B. to have

C. not to have

D. have