I don’t know why you’re always worrying about it. ___, you have nothing to do with it.

.People have planted a great many trees in order to _____ wind and sand in the desert.

Listen! Helen is singing in the classroom.—It _______ be Helen. She has gone to Shanghai.

Don’t him. He is busy writing an essay.

The book is well worth ______. Everyone ______ buy one and read it.