—Can I go to the park, Mum?
—Certainly. But you ______ be back by six o’clock.
A. can B. may C. might D. must
—I’m leaving now.
—______ you turn off the lights and the computer.
A. To make sure B. Make sure C. Made sure D. Making sure
The population problem may be ______ one of the world today.
A. the most B. most difficult C. the greatest D. more interesting
Don’t ______ so often. It’s bad for your health.
A. get up B. stay up C. look up D. come up
—Mum, when can I watch TV?
—As soon as your homework ______.
A. finish B. finished C. is finished D. will be finished
—I hear Mr. Zhang has gone to Beijing for a meeting.
—Really? Do you know when he ______?
A. leaves B. was leaving C. has left D. left
