You should understand the traffic rule by now. We have had it __________ often enough.
| A．explaining | B．to explain |
| C．explain | D．explained |
The manager listened to the customers’ complaints attentively with great patience, _____ to miss any point.
| A．not trying | B．trying not | C．to try not | D．not to try |
Never should we forget the war and sufferings _____ caused to the people.
| A．it | B．which | C．that | D．what |
As soon as his teacher begins lecturing, he begins to doze off, not intentionally but _____.
| A．personally | B．randomly | C．habitually | D．unconditionally |
The Chinese lunar New Year usually _____ two records: the world's most watched television gala show, and its busiest telecommunications network.
| A．develops | B．witnesses | C．establishes | D．launches |
Nowadays certain limit should be set on use of cars to reduce air pollution.
| A．/; the | B．a; the | C．the; / | D．the; the |