低压避雷器的接地电阻不宜大于（）欧姆。
A.4
B.10
C.15
D.30
参考答案：B
My school begins at 8 o'clock in the morning. So I have to ________ school before 7:50 a.m. [ ]
A. live at
B. finish
C. get to
D. leave
把灼烧减少固形物当作水中实际有机物的含量，这对含盐低的水，误差不大。（）
