-He's (reading in the library.)括号部分提问.What is he doing?
-Mary's singing in her room.改否定 Mary isn't singing in her room.
-The girls are dancing at school.改一般疑问
Are the girls dancing at school?
-He's (reading in the library.)括号部分提问.What is he doing?
-Mary's singing in her room.改否定 Mary isn't singing in her room.
-The girls are dancing at school.改一般疑问
Are the girls dancing at school?