There are several research centers in China ________ a certain disease called Bird Flu is being studied.
| A．which | B．where | C．when | D．what |
While he was at____ college, he took part in political activities, and was soon throw into ____ prison.
| A．the; / | B．/; the | C．/ ; / | D．the ; the |
I was in the baths , ______ I didn’t hear the telephone, which was ringing several times.
| A．as a result of | B．with the result that | C．resulting in | D．resulting from |
She was so _____ in her job that she didn’t hear anybody knocking at the door.
| A．devoted | B．attracted | C．drawn | D．absorbed |
Our professor told us that salt water _____ at a lower temperature than fresh water.
| A．is freezing | B．was frozen | C．freezes | D．froze |
Until recently historians assumed that calendars ________ with the advent of agriculture.
| A．came to existence | B．came to existing |
| C．came to exist | D．were existential |