一道高三英文选择题------pollution is the key to ----the country a com

问题描述：

一道高三英文选择题
______pollution is the key to ____the country a comfortable and clean place to live in.
A.To control; keep B.To control;keeping C.Control;Keeping D.Controlling; keep.
我知道答案是B.
但是想问一下为什么是B以及其他选项为什么不对.谢谢高手指点.

1个回答分类：英语 2014-12-02