i can't decide which to buy.为什么用to buy?buying可以吗

问题描述:

i can't decide which to buy.为什么用to buy?buying可以吗

不行,因为这句话中to buy 修饰which,而言buying是动名词,不可以修饰宾语.但不定式可以修饰宾语.
例子:
I wish him to be at the meeting.
They thought the moon to be inhabited.