为什么“I bought a book ."变为疑问句时动词为原型“buy”

为什么“I bought a book ."变为疑问句时动词为原型“buy” who bought a new bike yesterday?疑问句中动词不是用原型嘛?为什么这里用bought而不是 What( )you( )(buy)? I bought a comic book. (用所给动词的恰当形式填空) I bought a book 在这里 buy是不是短暂性动词吖 如果不是 那什么时候buy才是短暂动词吖 i bought a book three days ago.改为一般疑问句. 为什么i spent 5 yuan _this book.填buy,而不是to buy 或 bought? I read a book today.变为一般疑问句 I have a picture-book(变为一般疑问句) I bought him a book中的bought是什么系动词吗大神们帮帮忙 He is going to buy a book变为否定句和一般疑问句.做两种回答 I would like ____ a picture book.A.buying B.to buy C.bought 英语练习卷一.选择正确的动词形式填空：1. _______（buy,bought,buying) you a book