—The air pollution is terrible.
— It will be worse ________ we take action to protect the environment.
| A．if | B．unless | C．until | D．When |
Everyone should save every drop of water. Remember to _______the tap after you finish washing.
A. turn off B. turn down C. turn on
Our city is becoming nicer. Look! There are many trees and flowers on _______ sides of the streets.
A. all B. each C. both
We used to study in the old building_______ was broken down last year.
A. which B. where C. what
—How long _______it _______ you to work out such a difficult problem?
—About thirty minutes.
A. did… take B. does… take C. did…cost
Excuse me, sir. Could you tell me _______?
A. where can I get a post card
B. where I can get a post card
C. that I could get a post card