__ pollution is the key to __ the country a comfortable and clean place to live inA.To control; keepb.To control; keepingc.Control; keepingd.Controlling; keep为什么不选D呢,选哪个啊,
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
选a啦，动词不定式作主语表示还没开始进行的动作，后面是动词不定式表目的。
答
to control 表目的
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.
答
因为key to 后面应接名词或动名词，所以不选D, C中Control是动词原形，也不行， 只能选B