都是情态动词 变一般疑问句都把它提到句首 否定句后面都加not
Can could 能 可以 会 could 比can的语气委婉 也是它的过去式
I can swim
Can you swim ? Yes, I can. No I can't
I can't swim.
Could you give me an apple? Yes,I could. No, I couldn't .
Should 应该
We should stay healthy .我们应该保持健康
Should you stay healthy? Yes ,we should. No,we shouldn't .
must 必须
We must call a doctor.
Must you call a doctor? Yes. We must. No. We needn't . 注意它的否定回答用needn't
May 可能 语气特别的委婉
希望能帮到你 打字不轻松的说可以看出你是纯手打的 谢谢了顺便问一下 什么时候的否定回答是no ，we do not have to