题目内容：

I'm going to the supermarket,Tom.Is there anything special you'd like to eat?
No,I don't feel like eating,but ____ you pass a bookshop,you might buy me some books
A.if B.when Cwhile Das
为什么不能选when

优质解答

我去超市了,小汤姆,给你买点吃的吧?
我不饿啊,但是
a ,如果你路过书店,可以帮我买点书
when 表示一定要让此人路过书店的意思,不礼貌
if 比较矜持啊