第二部分：英语知识运用
第一节：单项填空（共15小题，每小题1分，满分15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. One day Chuck is on a flight across the Pacific Ocean _______ suddenly his plane crashes.
A. since B. when
C. while D. though
22. --- He works hard at English.
--- _______ and _______Joe.
A. So he is; so does B. So is he; so do
C. So he does; so is D. So he does; so does
