问题补充:
Is necessary them to stop every two hours?
A. that; for; resting
B. that; of; to rest
C. it; for; to rest
D. it; of; resting
答案:
A. that; for; resting
B. that; of; to rest
(答案→)C. it; for; to rest
D. it; of; resting
解析:it is necessary for sb to do sth “对于某人来说有必要做某事”,stop to do 停下来做另一件事,stop doing停止做某事,答案C。