Teenagers should learn to protect (保护) ______from all kinds of dangers.

I phoned you at 7:00 this morning. But there was no answer.—Well, maybe I _________ morning exercises at that time.

Listen! Can you hear someone ?

Mom, my classmates invited me ____ a field trip. May I go with them?—OK.

You look excited.–Yes, I ______ Hawaii with my friends.