第一节 语法和词汇知识（共20小题；每小题1分，满分20分）
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. Good technique in medicine means less pain and fewer deaths and, _____ it is our duty to master it.
A. altogether B. therefore C. otherwise D. however
22. In the office I never seem to have time until after 5:30 p. m. , _____ many people have got home.
A whose time B. that C. on which D. by which time
