Enough sleep is good for teenagers. — Quite right. If you for your favorite TV programs, you will feel sleepy.

English is a language that many people around the world _______not speak perfectly but _________at least understand．

____________ he has known the good news. —- ______ is no wonder he is so excited.

I don’t know he tomorrow. I think if he, I’ll go to see him.

Did you return from Shanghai on time?—No. The train________ I took was late because of the bad weather.