21._______ the teacher______ a burning candle, he helped the students to understand the function of teachers.
A. Compared; to B. Comparing; with
C. Comparing; to D. Compared; with
【解析】选C。compare A to B把A比作B，符合题意。compare A with B把A与B相比。另外，compare的逻辑主语应该和句子的主语he一致，且它们之间为主动关系，故应使用v. -ing形式。
22. —Can you give me the right answer?
—Sorry, I______ . Would you repeat that question?
A. hadn’ t listened B. haven’ t listened
C. don’ t listen D. wasn’ t listening
【解析】选D。考查时态。根据语境可知，对方在问问题的时候，“我”当时没有注意听，故用过去进行时，强调当时的情形。
