Where have you been?—I got caught in traffic, otherwise I _______ here earlier

Forty percent of the class _______ most of the work, and some of the work ______ really difficult.

Nancy is________dancing，and she keeps dancing till midnight every day.[ ]

I used to use English a lot and spent an hour each day _____ English books in the library.

Tom_____ Mary speaks good Chinese, so they can communicate with these Chinese students very well.