Do you know when your friend ___? –I’m not sure. I will tell you when he _____?

Can I see the headmaster at the moment, please ? — I’m afraid not. He _______out. He _____in 10 minutes.

In recent years，more and more Americans like traveling during holidays．—_______.

Now more and more people have realized that drugs do great harm to people’s health and their families. — Quite true, so everyone should them.

A number of foreigners learning Chinese.—Right. The number of them increasing little by little.