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 the face of ______ failure, it is the most important to keep up _____ good state of mind.
A. / ; a B. a; / C. the; / D. /; the
22.--- The floor is dirty. Can anyone clean it?
--- ______. I do it all the time.
A. Don’t mention it B. Why you? C. Not sure. D. Not me again.
