Busy as Tom is, exercise has always been______his work.

______ our team seems to lack at the moment is the determination to win the match．

He had a stomachache ________ he ate something bad this morning.

There ______ lots of bad information which is not ____ for teenagers on the Internet.

Look! Some of the children _____ in the river. —Oh, it’s dangerous to do that. We must _____ them.