问题
选择题
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
答案：C
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。