21．--She was in class on Friday afternoon, but no one has seen her ever since. --She ____an accident. A.must have B. might have had C. could have had D. should have had 22. --Would you mind my opening the window? --_____. A.Yes, please. B. No, please don’t. C. No, please yourself. D. Yes, if you like. 23. The whole book____12units, ____two mainly revisions. contains; including B. includes; containing C. contains; containing D. includes; including 24. She began to play table tennis ____, and became famous _____. A.in the 1970s; in her twenties B. in 1970s; in her twenty C. in the 1970s; in the twenties D. in the 1970s; in the twenty 25. Mr. Smith is a boss, ____ factory my uncle is working. A. in whose B. whose C. in whom D. of which