21.If you don’t put the food in the refrigerator, it may go ____.
A)off
B)over
C)wrong
D)out
22.If this university ____ such a good reputation, I would not have come here.
A)didn’t have
B)hadn’t had
C)doesn’t have
D)hasn’t had
23.He agreed with the plan in ____, but thought that in practice it would not work.
A)attitude
B)approach
C)viewpoint
D)principle
24.If only we ____ then the disease was curable.
A)knew
B)could know
C)had known
D)would have known
25.The weather is highly ____ at this time of the year and it is hard to know what to wear.
A)various
B)variant
C)variable
D)varied
26.Our company decided to ____ the contract because a number of the conditions in it had not been met.
A)destroy
B)refuse
C)assume
D)cancel
27.Eminent physicists from all over the world came to the U.S.to ____ the centennial(一百周年)of A.Einstein’s birth.
A)congratulate
B)applaud
C)celebrate
D)participate
28.Not until midnight ____him in the hotel.
A)we found
B)we did find
C)found we
D)did we find
29.I could just see a car in the distance, but I couldn’t ____what color it was.
A)make out
B)look to
C)look out
D)take in
30.High in the sky a ____ of birds was flying southward.
A)swarm
B)flock
C)crowd
D)herd