The young man stopped and looked back as if ______ whether he was being followed.
From my point of view,the theory thatby the scientist is not quite scientific.
Tom’s mother often requires that hemore time in studying English every day.
We can't go out,for it is getting dark and,it is raining.
Don't put your books everywhere.Keep them.
— I ____ to your birthday party last Sunday. — Unfortunately, you were out on business.