1 Mary ( is swimming ) in the pool now .
否定句,Marry isn't swimming in the pool now .
一般疑问句,Is Marry swimming in the pool now
肯定回答：Yes,she is
否定回答,No,she isn't.
划线部分提问 What is Mary doing now?
2 My father's friend ( is dancing ) in the room now.
否定句,My father's friend isn't dancing in the room now.
一般疑问句,Is your father's friend dancing in the room now?
肯定回答：Yes,he is .
否定回答,No,he isn't.
划线部分提问 What is your father doing in the room now