There are so many kinds of pens in the shop ,I can’t decide .
A. when to buy
B. where to buy
C. what to buy
D. which to buy
网友回答
A. when to buy
B. where to buy
C. what to buy
(答案→)D. which to buy
解析：根据前半部分的意思“商店中有如此多的钢笔”可知，后半句的意思应该是“我不能决定选哪一枝”。ABC都与题干的意思不符，所以本题选D。