“Where’s my book? I can’t find it”.“It _______ on your desk.”

 — How’s your tour around the North Lake? Is it beautiful?— It ______ be, but it is now heavily polluted.

—________ we finish the work before class, Jack?—No, we_________ . We can do it after class.

Just because Tom has made some mistakes, _____you follow that he is a bad boy? 

---- Is Ann knocking at the door?--- No, it ______ be Ann. She has gone to Beijing.