第一节：单项填空(共15小题：每小题1分, 满分15分)
21. In general, the old man is generous. But ______, he was mean to an old beggar.
A. at once B. once again C. for once D. once over
22. The speech by the mayor of Shanghai before the final voting for EXPO 2010 is strongly impressed _____ my memory.
A. to B. over C. by D. on
23. Nancy asked Smith to take tea with her. He ______, fearing to cause her inconvenience.
A. ignored B. declined C. resisted D. cancelled
