— Do you know where Mary is? I couldn’t find her anywhere. — Well . She        have gone far—her coat’s still here.

This book _____ Lucy’s. Look! Her name is on the book. 

--Have you decided where to go for your summer vacation? --Not yet. We_________ go to Mount Lu. It is a good place for vacation.

–Look at that girl! Is it Susan? --No, it _______ be her. She has gone back to her hometown.

All of us must do_______ to help protect the environment，or we will have more hazy weather雾霾天气.