Great as Newton was, many of his ideas_____today and are being modified by the work of scientists of our time.
| A．are to challenge | B．have challenged |
| C．are challenging | D．have been challenged |
One third of the country __________ covered with trees and the majority of the citizens __________ black people.
| A．is; are | B．is; is |
| C．are; are | D．are; is |
Japan's refusal to release __________ Chinese fishing boat captain had already caused __________ damage to Sino-Japanese bilateral contacts （双边关系）.
| A．the; 不填 | B．a; 不填 |
| C．a; a | D．the; the |
William found it increasingly difficult to read, for his eyesight was beginning to __________.
| A．disappear | B．fall |
| C．fail | D．damage |
It is generally believed that constant reading and comprehending can __________ our mental ability of comprehension while physical exercise can help build up our body.
| A．stress | B．effect |
| C．strengthen | D．decide |
__________ in a university in the U. S. A.，Chinese students must have excellent speaking and writing abilities in English.
A. EducateB. Being educated
C. To be educatedD. Having educated