21. After ______silence of several minutes, he came towards her and said, “I have struggled with my feelings , but without ______success!”
A. a; the B. the; a C. 不填; a D. a; 不填
22．Knowing _____, as a matter of fact, one shouldn’t know is a terrible thing．
A．whether B．that C．what D．when
23．_____ he met with the terrible difficulty did he realize the importance of my advice．
A．Even though B．Only before C．Never until D．Ever since
