第一节 单项填空（共15小题，每小题1分，满分15分）
请从A、B、C、D四个选项中，选出可以填入空白处的最佳选项，并在答题卡上将该选项的标号涂黑。
例：A computer can only do _____you have instructed it to do.
A. how B. after C. what D. when 答案是C。
21. When I saw the beautifully decorated house, I really wondered ______ she could manage that all by herself.
A. why B. when C. where D. how
