People take naps at noon in warmer climates, ____ the heat makes work difficult in the early afternoon.
| A．which | B．what | C．where | D．when |
Mary has __________ herself __________ for the party.
| A．held; up |
| B．attended; to |
| C．done; up |
| D．turned; up |
I __________ the names of plants.
| A．familiar with |
| B．are not familiar to |
| C．am not familiar as |
| D．am not familiar with |
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 |