---How can I keep healthy?---I think you ought to_________.A.do more exerciseB. doing more exerciseC. exercising more
He the book to the library if he it tomorrow.
We some robots in the next few months, and there some in the office, too.
Beijing a lot in the past ten years. Now it has become one of the biggest modern in the world.
---Let’s go fishing if it ________this weekend. ---But nobody knows if it ___________.
I didn’t hear the phone because my father__________TV then.