----Why does your teacher _________ play basketball?-----Because he does not have much free time to play it.
None of us _____ running, but we all like swimming.
He is tall, _____ his son is short.
What can we students do _____ the environment?
There are five people in the room, but I know _____.
—What did our geography teacher say?—She told us that the earth _____ around the sun.