情态动词用法
只要将情态动词移到主语(Subject)的前面，句尾加上问号。这样就成了疑问句。
1. She can work. (主语she, 情态动词 can，动词 work)
Can she work ? (这就是疑问句）
2. He would be working. (主语he, 情态动词 would，动词 be working) Would he be working ?
3. They should have worked. (主语they, 情态动词should, 动词have worked)
Should they have worked ?
4. I could have been working. (主语 I, 情态动词 could, 动词 have been working)
Could I have been working ?
三、情态动词的否定句：
在情态动词的后面加上 not 就成了情态动词否定句。
1. She can work.
She cannot work. (注意：can 和 not 须连在一起）(这就是否定句)
2. He would be working.
He would not be working. (would not)
3. They should have worked.
They should not have worked. (should not)
4. I could have been working.
I could not have been working. (could not)