Every Friday is the school open day , __________ parents can go to the class to observe it .
| A．where | B．when | C．whose | D．which |
The bus was due to __________ at 5 p. m.，but it arrived one hour late due to __________ by the heavy fog.
| A．arrive; be held up |
| B．arrive; being held up |
| C．arriving; be held up |
| D．having arrived; having been held up |
The professor devoted all his life __________ the treatment of AIDS.
| A．to research |
| B．in researching |
| C．to researching |
| D．at researching |
He was __________ down for several days after he heard the bad news.
| A．broken |
| B．cast |
| C．cut |
| D．discouraged |
They all looked down upon him. He was __________ a singer.
| A．not more than |
| B．less than |
| C．no more than |
| D．more than |
In the experiment we kept a watchful eye __________ the development and recorded every detail.
| A．with |
| B．on |
| C．for |
| D．to |