空气在矿井井巷重流动时,井巷阻止空气流通的反作用力称为()。
参考答案:通风阻力
Can you tell me _____ just now? [ ]
A. where did you go
B. where you go
C. where you went
D. where do you go
斯氏位投照时,要求()
A.听眦线与胶片垂直
B.听鼻线与胶片垂直
C.瞳间线与胶片垂直
D.听眶线与胶片垂直
E.以上都不对