26．We are both looking forward to _____ next week. 　A. going on vacation 　　　　　　 B. go on vacation 　C. be going on vacation　　　　　 D. have gone on vacation

25．Only one of these books is _____. 　A. worth to read 　B. worth being read　 C. worth of reading 　D. worth reading

24．Don't forget _____ this book to John when you see him. 　A. to return 　　　 B. returning　　　　 C. return 　　　　　　 D. to returning

23．The scientist suggested ____ the experiment in a different way.

　 A. do　 B. to do　 C. doing　 D. done

22.Seeing is _________.

　　 A. to believe　 B. believing　　　 C. believed　 D. being believed

21.__________ clean is a safeguard against disease.

　　 A. To be keeping　 B. Kept　　　 C. Keep　　　 D. Keeping

20.What about _________ to the concert with us ?

　　 A. we go　　 B. we going　　 C. going　　　 D. to go

19.The story was so funny that we ___________.

　　 A. couldn't help laugh　　　　　 B. can't but laugh

　　 C. couldn't help laughing　　　　 D. couldn't help but to laugh

18.His parents insist on ____________ to college.

　　 A. he should go　 B. he go　　　　　 C. his going　　　 D. him to go

17.Keep on _________ and you will succeed.

　　 A. a try　　　　 B. try　 　　　　　C. triing　　　　　 D. trying