The teacher said that Columbus _______America in 1492.
| A．discovered | B．found | C．had discovered | D．had found |
While watching television, ____.
| A．the doorbell rang | B．we heard the doorbell ring |
| C．there was someone knocking at the door | D．the doorbell was ringing |
I’ll have all of the readings ____ by the end of this term if my plan goes well.
| A．completing | B．to complete | C．completed | D．being completed |
—How did it come that you damaged your car so badly?
—I ____into a tree on the roadside the other day.
| A．ran | B．had run | C．was running | D．run |
Air pollution, together with littering, ____ many problems in our large industrial cities today.
| A．causes | B．cause | C．caused | D．causing |
His advice made me happy, but ____others angry.
| A．making | B．to make | C．/ | D．make |