21. ----Has he arrived 　　　　?　　 ---- 　　　　.

　　　　 A. yet, Not already　　 B. yet, Not yet.　　 C. already, Not already

20. He has 　　　　Beijing three times.　 He has 　　　　there again.

　　　　 A. been to, gone　　 B. been, gone to　　 C. gone to, been

19. 　　　　you afraid of dogs?

　　　　 A. Be　　 B. Are　　 C. Do

18. He has never 　　　　trees down.

　　　 　A. cut　　 B. cuts　　 C. cutted

17. Have you littered things 　　　　？

　　　　 A. about　　 B. on　　 C. into

16. He with his group 　　　　gone to plant trees.

　　　　 A. has　　 B. have　　 c. had

15. 　　　　you live, you should protect the environment.

　　　　 A. Where　　 B. when　　 C. wherever

14. 　　　　care of the environment 　　　　important.

　　　　 A. Take, are　　 B. Taking, is　　 C. To take, are

13. He has been here since 　　　　.

　　　　 　A. five years ago　　 B. five years before　　 C. five years

12. He has studied here for 　　　　.

　　　　 A. five years　　 B. five years long　　 C. five year ago