It is important for us___________ Chinese history.
—The classroom is ____ clean ____ it was yesterday.— Sorry, I forget to clean it.
I was just falling asleep ____ there was a loud knock at the door.
----Can you tell me if he ________ ?----If he _________, I will call you.
There are many shops on ________ side of the street.
The policeman warned the driver _______too fast. It was very dangerous.