Listen! Mary           in the next room.

Listen! Mary           in the next room.

A．sings             B．is singing          C．sang             D．sing

Listen! Mary           in the next room.

1. A.
   sings
2. B.
   is singing
3. C.
   sang
4. D.
   sing

Listen! Mary ________ in the next room.

[　　]

A．sings　　　　　　　　B．is singing

C．to sing　　　　　　　 D．is sing