She doesn’t want to do it; we have to find ____ to do it.

Which is ________ to learn, singing or dancing, baby?

Look, there_____ many birds around here, but now we hardly see them. What a pity!—Yeah! The air pollution has caused the problem!

Teenagers must_______ the computer games.

Whitney Houston’s sudden death suggests that drug abuse is such a serious problem ______ we should deal with properly.