提醒：情态动词后面的行为动词用原形。
情态动词具体包括can，may，must，could，should，would等。
1、情态动词构成的陈述句
I can
You can speak English.
He（She） can
We can
You can speak English.
They can
2、情态动词构成的否定句
I can't
You can't speak English.
He（She） can't
We can't
You can't speak English.
They can't
3、情态动词构成的一般疑问句
Can I
Can you speak English?
Can he（she）
Can we
Can you speak English?
Can they
情态动词构成的一般疑问句及肯定回答和否定回答。
Can I speak?
Yes, you can.
No, you can't.
Can you speak?
Yes, I can.
No, I can't.
Can he（she,it） speak?
Yes, he（she,it） can.
No, he（she,it） can't.
Can we speak?
Yes, we（you） can.
No, we（you） can't.
Can you speak?
Yes, we can.
No, we can't.
Can they speak?
Yes, they can.
No, they can't.