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. ---- Hey, you haven’t been acting like yourself. Everything Ok ?
----- _________ .
A. I am fine, thanks B. Sure, it is C. That’s good D. It’s Ok
22.------ I hear the workers in this factory get paid by ____ week.
----- That’s right . Most of them get about 300 yuan _____ month.
A. / ; a B. the; / C. a; the D. the; a
