26. We agree to accept _________ they thought was the best tourist guide.
A. whatever
B. whomever
C. whichever
D. whoever
27. Although many people view conflict as bad, conflict is sometimes useful _________ it forces people to test the relative merits of their attitudes and behaviors.
A. by which
B. so that
C. in that
D. provided that
28.A beam of light will not bend round corners unless _________ to do so with the help of a reflecting device.
A. made
B. being made
C. having made
D. to be made
29.A knock at the door again! It was the third time someone _________ me that evening.
A.has interrupted
B. had interrupted
C.to have interrupted
D. would have interrupted
30. The government agrees to install services _________ by residents over a ten-year period.
A. which are to be paid for
B. for which to be paid
C. which to be paid for
D. to be paid for which
