第二部分英语知识运用(共两节，满分35分)
第一节单项填空(共15 题,每小题1分,满分15分)
请认真阅读下面各题,从题中所给的四个选项A、B、C和D中,选出最佳选项。并在答题卡上将该选项涂黑。
21. So involved in his teaching business _______ that he can hardly accompany his family at weekends.
A. has Mr. Wang become B. has become Mr. Wang
C. Mr. Wang has become D. become Mr. Wang
