is necessary for you to lock the car when you don’t use it.A. WhatB. ThisC. ItD. That

问题补充：

is necessary for you to lock the car when you don’t use it.

A. What

B. This

C. It

D. That

答案：

A. What

B. This

(答案→)C. It

D. That

解析：考查固定句型：it is+adj/n+to do,it是形式主语，不定式是真正的主语，句意：对你来说不用的时候把车锁上是很必要的。选C。