Which dress do you like best, madam?
Sorry, I cant decide_____now.
A. to buy which one
B. which one to buy
C. buy which one
D. which I should buy it
老师，这个是动词不定式，答案是选B，为何不选A, 谢谢。
Which dress do you like best, madam?
Sorry, I cant decide_____now.
A. to buy which one
B. which one to buy
C. buy which one
D. which I should buy it
老师，这个是动词不定式，答案是选B，为何不选A, 谢谢。
【答】在英语中，动词不定式可以放在疑问词或 whether（是不是）后面，不可以放在它们的前面。所以，这道题的答案是B，不可以选A和C。
D. which I should buy it 中，which 是 should buy 的宾语，it 是多余的，所以也不可以作为答案。
【例句】 I wonder who to invite. 我拿不定主意该邀请哪个。/ Tell us what to do. 给大家说说该干什么。/ Can you show me how to get to the station? 请问去车站如何走。/ I dont know where to put the car. 我不了解该把车子停在哪儿。/ Tell me when to pay.告诉我什么时间付款。/ I cant decide whether to answer her letter. 我拿不定主意是不是该给她回信。（但不可以说：I cant understand why to do it.）（摘自《牛津英语使用方法指南》第三版286节）
