2. We are________ ( 研究 ) how to improve English.

1.Many animals died for different ___________( 原因 ) .

20. Stop _______ . It’s time for class.

　　　 A. talk　　　　　 B. to talk　　　 C. talking

19. you had better finish _______ your homework.

　　　 A. do　　　　　 B. doing 　　　C. to do

18.What about ________ a cup of tea?

　　　 A. have　　　　　　 B. having　　　 C. to have

17.He is busy practicing ___________English.　

　　　 A. speaking　　 B. to speak　 C. speak

16. You had better _______ your homework carefully.

　　　 A. going　　　　　 B. to do　　　 C. do

15. Let me___________. Don’t make me ____________.

　　　 A. go .... cry　　 B. go... to cry　　 C. going ... crying

14. Why not _________ there with me?

　　　 A. go　　 B. going　　 C. to go

13．(　　 )How about ________to the park .

　　　 　　 A．take B．to take 　　 C．taking