候车室原则上（）消毒、杀虫、灭鼠一次。
A.每月
B.每两个月
C.每季度
D.每半年
参考答案：C
Some people try to knock me down, only______ me more determined to do better. [ ]
A. to make
B. makes
C. having made
D. made
流量标准装置可以进行标准流量计的性能试验研究工作
