之前介绍句型转换的时候，告诉过大家一个排序。现在进行时由am/is/are +V.-ing构成, 也适用这个规律。

例1

肯定句：I am reading a book.

否定句：I am not reading a book.

一般疑问句：Are you reading a book?

肯定回答：Yes, I am.

否定回答：No, I’m not.

特殊疑问句：What are you doing?

例2

肯定句：He is dancing.

否定句：He is not dancing.

一般疑问句：Is he dancing?

肯定回答：Yes, he is.

否定回答：No, he isn’t.

特殊疑问句：What is he doing?

例3

肯定句：They are playing basketball now.

否定句：They are not playing basketball now.

一般疑问句：Are they playing basketball now?

肯定回答：Yes, they are.

否定回答：No, they aren’t.

特殊疑问句：What are they doing now?