Ⅱ. 单项填空(共15小题; 每小题1分，满分15分)
21. —John was late for Mary’s English class this morning.
—______? As far as I know, he never came late for class.
A. So what B. Why not
C. What for D. How come
【解析】选D。so what那又怎么样；why not为什么不；what for为什么；how come怎么回事。D项符合题意，即“他怎么会迟到呢？据我所知，他从来都没有迟到过”。
