根据所给单词的适当形式填空。

小题1:Our Chinese teacher asked us to write a 400-word __________ （composition）about the autumn. I think it’s easy.

小题2:—What has_________(happen) to your hometown recently?

—Great changes have taken place.

小题3:We have taken some _________(measure) to look for the lost boy. We can find him in danger.

小题4:We have ________(learn) a lot of knowledge from the wonderful trip.

小题5:Not all people know that light pollution does great __________ (harmful) to human’s health.