---Don’t you know Zhang Tao in my office? --- _______ He is my friend.A. Yes, I do. B. No, I don’t. C. Yes, I am
There is _____ pollution in the world. We must stop it.
The cleaners must prevent the street ______.
None of us _____ running, but we all like swimming.
He is tall, _____ his son is short.
What can we students do _____ the environment?