阅读下面短文，掌握其大意，从每题所给的A、B、C、D四个选项中，选出最佳选项。
Perhaps the most interesting person I have ever met is an Italian professor of philosophy who teaches at the University of Pisa. ___21___ I last met this man eight years ago, I have not forgotten his special qualities. First of all, I respected his ___22___ to teaching. Because his lectures were always well-prepared and clearly ___23___, students crowded into his classroom. His followers liked the fact that he believed in what he taught. Furthermore, he could be counted on to explain his ideas in an ___24___ way, introducing such aids to understanding as oil paintings, music, and guest lecturers. Once he ___25___ sang a song in class in order to make a point clear. Secondly, I admired the fact that he would talk to students outside the classroom or talk with them ___26___ the telephone. Drinking coffee in the cafe, he would easily make friends with students. Sometimes he would ___27___ a student to a game of chess. Other times, he would join students groups to discuss a variety of ___28___: agriculture, diving and mathematics. Many young people visited him in his office for ___29___ on their studies; others came to his home for social evenings. Finally, I was attracted by his lively sense of humor. He believed that no lesson is a success ___30___, during it, the students and the professor ___31___ at least one loud laugh. Through his sense of humor, he made learning more ___32___ and more lasting. If it is true that life makes a wise man smile and a foolish man cry, then my friend is indeed a wise man.
21. A. Although B. When C. Even if D. Now that
22. A. attention B. introduction C. relation D. devotion
23. A. held B. delivered C. attended D. written
24. A. imaginative B. ordinary C. opposite D. open
25. A. also B. nearly C. even D. only
26. A. with B. by C. from D. on
27. A. invite B. lead C. prefer D. show
28. A. questions B. subjects C. matters D. contents
29. A. ban B. agreement C. dependence D. advice
30. A. for B. until C. since D. unless
31. A. hear B. suggest C. share D. demand
32. A. helpful B. enjoyable C. practical D. useful
