煤巷掘进和采煤工作面应保留的最小预测超前距离均为()m.。
A、3
B、2
C、1
参考答案:B
There was a chance in a million that she might be right. Which of the following phrases can be used to replace “a chance in a million”?[ ]
A. the scarcest chance
B. the greatest chance
C. the remotest chance
D. the lightest chance
怎样鉴别刮板链的松紧程度?