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。
21. I need another dictionary because ________ cover is dirty and ________ page is missing.
A. a ; a B. a ; the C. the ; a D. the ; the
22. This cake is very sweet. You ________ a lot of sugar in it.
A．should put B．could have put C．might put D．must have put
23. — Professor Wang, thank you so much for giving us this wonderful speech.
— ________
A. It doesn’t matter. B. That’s right.
C. Never mind. D. My pleasure.
