问题补充：
There are so many kinds of Mp4 in the shop. We can’t decide .
A. to buy what
B. what to buy
C. to buy which
D. which to buy
答案：
(答案→)A. to buy what
B. what to buy
C. to buy which
D. which to buy
解析：句意：商店里有各种各样的MP4。我们不能决定买哪个。本题考查的是特殊疑问词+动词不定式的结构。因为在商店里有许多MP4，所以不知道选择哪一个。因此是which to buy。故选A.
