28.　 B look forward to doing sth. / sth. 表示“盼望做某事”，而look forward to do sth.表示向前看目的(要做。。。)

27.　 A　 定冠词the加上表示时间的名词起连词作用，引导时间状语从句。如the night/ the minute/ the spring/ the year等。

26.　 C

25.　 C

24.　 D

23.　 C

22.　 B

21.　 C　 句中有连词that和谓语must be stimulated，缺少一个谓语动词，排除A,D，该句译成汉语是“有。。。的证据”,而不是“它是。。。的证据”所以排除B.

20.　 D on which to base his arguments in favor of the new theory = The professor will base his arguments in favor of the new theory on sufficient grounds.

19.　 B