---Fifty dollars for such a T-shirt! You _______ be joking!---I’m serious．It’s made of silk.

Cars, buses and bikes ________ stop when the traffic lights turn red.

- Tom, where is your father?- I’m not sure. He _______ in his office.

— Dad, must we wait until the light becomes green? — Yes, I’m afraid we ______. That’s the traffic rule.

---Never touch my computer while I’m away． --- Sorry,  __________.