I was out of town at the time，so I don’t know exactly how it ________.
| A．was happening | B．happened |
| C．happens | D．has happened |
John was so sleepy that he could hardly keep his eyes ______.
| A．open | B．to be opened | C．to open | D．opening |
— Has Jack finished his homework yet?
— I have no idea；he ＿＿it this morning.
| A．was doing | B．had been doing | C．has done | D．did |
______ leaves the room last ought to make sure that the windows are closed and the door locked.
| A．Whoever | B．Who | C．Who will | D．Those who |
We should think of ways to stop the waste from the factory _____ our living environment.
| A．being polluted | B．polluting | C．from being polluted | D．polluted |
The mistakes made by Chinese students are quite different from ________made by the Japanese students in English study.
| A．That | B．which | C．what | D．those |