问题补充：
There are so many kinds of radios in the shop. I can’t decide .
A. to buy what
B. to buy which
C. which to buy
D. when to buy
答案：
A. to buy what
B. to buy which
(答案→)C. which to buy
D. when to buy
解析：句意是：商店里有如此多的收音机，我不能决定买哪一个。动词decide后面一般情况是接动词不定式作它的宾语，但是本题的要求是考查“疑问代词＋不定式”结构作宾语的现象。所以A和B错，前面的“There are so many kinds of radios in the shop”句子提供了选择的范围。只能用which, 所以答案是C。
