21. ---What has happened here?

---There was _______accident here about an hour ago, ______ car hit a tree and ______ driver was killed.

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

22. ---I’m not good at basketball, you know.

----_______. We’re playing for fun. Just try and you’ll see you can do it.

A. Well, it depends.  B. Take your time.  C. Come on!          D. That’s OK.

23. ---Did you find the missing couple in the mountain yesterday?

---No, but we _______to get in touch with them ever since.

A. have tried          B. have been trying   C. had tried         D. had been trying