Tom________tell the truth to his boss because he didn't want to make trouble.

 Don't use water to put out the fire if oil catches fire. As is known, oil ________ float on water.

 The chairman ________ hold office for five years according to the constitution.

—I’m afraid you missed a fantastic lecture yesterday. How come you were absent from it?—If you _______ know, I asked for a day off and visited a relative of mine in hospital.

Why _______ you be so stubborn? You should think over my advice on this matter.

Keep up a good state of mind even if you ______ fail plenty of times.

Lora，you ____________ leave all your books on the floor like this!

—Did Ann fail in English?—She ____. Don't you notice that she looks depressed?

 --My computer ____start, no matter how hard I try.--It might have crashed.

 —What did you say to your sister? I saw her crying in the room.— It _________ my fault. I just said hello to her when I met her, nothing else.

— Mr. Wang, I got zero on Answering Sheet One. Could you help me correct it?— I’m sorry, but it ______ be marked by the machine. Mark your test number with a pencil 2B next time.

---- What are you going to do this weekend?---- I don’t know. I      go to Beihai Park.

The new supermarket announced that the first to purchase goods on the opening day_______ get a big prize.

---Why not wear your miniskirt, Rose? --- Well, my legs are too thick, if you ______ know.

In China, you _____ vote when you are 18.

-----Could I have a look at your i-phone5s, dad?------Oh, dear, if you_______.

—You must have met him the other day.　　—Oh, no, I ________.

In case you ______ still have anything to offer, please contact our manager while he is available．

 I’m as busy as a bee; ________ you bother me with so many questions now?

Overloaded with work, school teachers now get far less sleep than they ______.