Câu hỏi: My elder sisters, both of them were doctors, said they were too busy to pick me up.

A. elder

B. both of them

C. too busy 

D. to pick

Câu 1: 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 2: Students suppose to read all the questions carefully and find out the answers to them.

A. suppose

B. all the

C. all the questions

D. them

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: If they took their language lesson seriously, they would be able to communicate with the locals now.

A. took

B. seriously

C.  would be

D. with the locals

Câu 5: The world is becoming more industrialized and the number of animal species that have become extinct have increased.

A. industrialized

B. species

C. extinct 

D. have

Câu 6: 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