22.---May I smoke here?

　 --- If you ________, choose a seat near the window.

　 A. should　　　 B. could　　　　 C. may　　 D. must

第一节 　单项填空(共15小题；每小题1分)

21.--- How’s your tour around the North Lake? Is it beautiful?

　 --- It ________ be, but it is now heavily polluted (污染).

　 A. will　　 B. would　　 C. should　　 D. must