从A、B、C、D四个选项中，选出可以填入空白处的最佳选项，并在答题卡上将该项涂黑。
21. At the end of the cross-talk, __ audience present in the hall burst into ___ laughter.
A. an ; the B. the ; a C. an ; / D. the; /
22. A troop _____fine weapons are marching towards the front.
A .are equipped with B. to be equipped with C. equipped with D. being equipped with
23. This stranger is familiar _________this area.
A. to B. for C. with D. in
24. He watched her, _________.
A. fascinating B. fascinated C. being fascinated D. having fascinated
