--- May we leave the classroom now? --- No, you ____________ . You ____________ to leave before the bell rings.

—Listen ! Helen is singing in the next room.—It _______ be Helen. She has gone to Beijing.

If prices rise too high, the government has to do something _________ it. 

-Why ________ it rain at weekends?-Never mind, let’s watch TV at home.

 —I’ll call Bob and tell him the good news.—You __________ do that. He was here just now and heard it.