He has read many books on history, so it’sfor him lo answer these questions.

We should pay close attention to safety in schools because of frequent reports about accidents ____ students got injured or killed while in school.

Tony lost his wallet. He didn’t talk to __________ all the afternoon.

Last summer I took a course on _______ poisonous gases.

Look, what’s _____ the tree?—A bird. It is _____there.