Câu hỏi: 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 1: The office manager insists that his staff use all of their vacation time, but he hardly never takes a vacation himself.

A. insists

B. use

C. their

D. hardly never

Câu 2: 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 3: 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 4: Mary and her sister just bought two new winters coats at the clearance sale.

A. her sister

B. just bought

C. two new

D. winters

Câu 5: 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 6: Mercury and alcohol are widely used in thermometers because their volume increases uniform with temperature.

A. are

B. widely

C. their volume

D. uniform with