II. 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. We have all experienced occasions _________ we have spoken our minds to someone, telling them exactly what we feel.
A. where B. which C. that D. when
22. __________ for my illness, I would have lent him a helping hand.
A. Not being B. Had it not been C. Without being D. Not having been
23. The resources on geography can be __________ in the State Library.
A. acquired B. required C. inquired D. requested
