一般监测井在液面下（）处采样。
A、0.1~0.3m
B、0.2~0.4m
C、0.3~0.5m
D、0.4~0.6m
参考答案：C
选择填空。
You ______ look out of the window in class. [ ]
A. aren't
B. don't
C. mustn't
D. wouldn't
支架阀件弹簧的塑性变形不得大于（）。
A.5%
B.6%
C.8%
