无害细菌约占细菌总数的（）以上。
A.50%
B.60%
C.70%
D.80%
参考答案：C
—Why are you so depressed?
—I _____ my MP4 player on the bus.
A．had lost
B．am lost
C．have lost
D．was lost
What do you often have______ supper? [ ]
A. at
B. for
C. to
D. with
