Not everyone has realized what ________important partthe balance of ________nature plays in their life.

David is taller than ________ in his class.

When you take the ice into a warm room, it becomes_________.

The government________air quality in urban areas from levels one to five: excellent, fairly good, slightly polluted, poor and dangerous.

I’m worried about the coming test. —You should work hard for it,_____you’ll have to take it again.