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. In memory of China’s Youth’s Day, ________ celebration took place on our campus. It was _______ success.
A. a; a B. the; the C. a; / D. the; a
22. Close friends are those ______ you feel so close that it is hard to imagine life without them.
A. to whom B. with whom C. by which D. in which
