Câu hỏi: It is difficult to write rules that tell exactly when we should apologize, and it is not difficult to learn how to do it.

A. difficult

B. that

C. when

D. and

Câu 1: The developing of the submarine was hindered by the lack of a power source that could propel an underwater vessel.

A. developing

B. the

C. a power

D. could propel

Câu 2: By the turn of the century, most of the inventions that were to bring in all the comforts of modern living has already been thought of.

A. By the turn of

B. that

C. were to

D. has already been

Câu 3: The guide told the tourists that it was a good restaurant specializing in seafood just round the corner from the museum.

A. The

B. it was a

C. specializing

D. just round

Câu 4: Doctors believe there is better in this modern world of ours to try to prevent illnesses than to rely on medicines to cure them.

A. doctors

B. there is

C. of ours

D. to

Câu 5: Not one in one hundred children exposed to the disease are likely to develop symptoms of it.

A. not one

B. are

C. symptoms

D. it

Câu 6: Each of the nurses report to the operating room when his or her name is called.

A. of the

B. report

C. his or her name

D. is called