What can we students do _____ the environment?

He is tall, _____ his son is short.

None of us _____ running, but we all like swimming.

The cleaners must prevent the street ______.

There is _____ pollution in the world. We must stop it.

I can’t stand _____ for you so long.

Students ought ______ the truth.

Teachers’ job is ______ the students learn well.

I have _______ to tell you.

-----Lin Tao’s spoken English is very good.

----- _______. He often talks with foreigners.