— I can’t get through to the general manager’s office.—The line is busy. Someone ________ the telephone.

---Guess what! I have got the highest score in the final exam. ---- Great! You ______ worked very hard and put a lot of energy into it.

--Is the man standing outside the teacher’s office Mr. Zhou?  --No, it ______ be him. He has gone to Hong Kong for an academic conference. 

—Do you think the phone is genuine(真品)? —I don’t think it ______ be a fake, as this shop has a very good reputation. 

The public transportation is very convenient in that big city , so there______be any difficulty in traveling around .