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,并用铅笔把答题卡上对应题目的答案标号涂黑.
21.Please wait for a moment. Our headmaster _________ to see us.
A. was coming B. came C. is coming D. has come
22. ——Excuse me, but can you tell me the way to the post office?
——Sorry. This is the first time that I ________ here.
A. was B. had been C. am D. have been
