21.   Something else I’ve greatly enjoyed is working as _____ peer mediator, someone who helps _____ students to settle problems that they have with other students.

A. the; the            B. /; /           C. a; the                     D. a ; /

22.---I’m terribly sorry for being late. My car broke down on the way.

---_______. I’ve just arrived .

A. That’s right                 B. That’s all right

C. All right                    D. Don’t mention it.