__ pollution is the key to __ the country a comfortable and clean place to live in
问题描述：
__ 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
为什么不选D呢,选哪个啊,
答
答案是 B the key to 中to 介词,后跟动词的ing形式,只能选B ,to control 是不定式作主语.