一、找be动词（am is are，was were）有则直接提前；
eg1. He is / was a teacher. ＝＞ Is / Was he a teacher? 肯Yes, he is/was 否No, he isn’t/ wasn’t.
二、无be动词，则再找情动(can may should must need)有情动则直接将其提前；
eg2.I can play soccer. ＝＞ Can you play soccer? 肯Yes, I can 否No, I can’t. (注:can’t容易多写n)
注：need有可能不是情态动词，怎么判断？＝＞根据 “情态动词+V原”的共性。
因为： need ①、情态动词：“需要”，后接: V原 ②、实义动词：“需要”，后接：sth 或 to do sth.
eg3. You need see a doctor. ＝＞ Must I see a doctor? 肯Yes, you need. 否No, you needn’t.
eg4. You need to see a doctor. ＝＞ Do I need to see a doctor? 肯Yes, you don’t. 否No, you don’t.
