第一节：单项填空: 从A、B、C、D四个选项中，选出可以填入空白处的最佳选项。(共22小题；每小题1分，满分22分)。

21. They ________ the foreign affairs those days.

　 A. engaged themselves in　　　　　　　　 B. were engaged to

　　 C. were engaged on　　　　　　　　　　　 D. were engaged with