Câu hỏi: Proteins are made up of folded irregularly chains, the links of which are amino acids.

A. made up of

B. folded irregularly

C. the links

D. which

Câu 1: Tom said that he was trying to carry out some campaigns to protect environment and will encourage others to do so.

A. he was trying

B. some

C. campaigns

D. will

Câu 2: A smile can be observed, described, and reliably identify, it can also be elicited and manipulated under experimental conditions.

A. identify

B. experimental

C. can also

D. A smile

Câu 3: The bones of the elderly are more prone to fractures than of young people.

A. the elderly 

B. more

C. to

D. of

Câu 4: My sister told me that she had met my teacher at the supermarket yesterday.

A. My sister told

B. had met

C. at the supermarket 

D. yesterday

Câu 5: The number of students attending universities to study economics have increased steadily in the last few years.

A. of students

B. attending

C. economics

D. have

Câu 6: Henry David Thoreau was an American writer who is remembered for his faith in religious significance of the nature.

A. an

B. is

C. for

D. the nature