一、单项填空（共15小题；每小题1分，满分15分）
从每题所给的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. I’m sorry to have forgot to pay back the money you lent me a month ago-________.
A. No hurry B. Forget it C. That's right D. Take it easy
22. It was half past eleven ________she came back last night, which made her mother angry____.
A. when B. that C. while D. since
