There're so many kinds of CD players on sale that I can't make u

There're so many kinds of CD players on sale that I can't make up my mind __________ to buy.
A、what
B、which
C、how
D、where
【正确答案】：B
【题目解析】：句意：有很多种CD播放机在打折，我不知道该买哪种​