Cast iron and gunmetal fittings are used freely in small sizes at moderate pressure; large
A. east iron firings
B. mild steel fittings
C. small fittings
D. large fittings
铀矿井总入风风流的粉尘控制浓度应不大于()/m3。
A. 0.02mg
B. 0.2mg
C. 2.0mg
D. 20mg
牛恒齿式为()
A. 2[0033(上)/4033(下)]=32
B. 2[3142(上)/3143(下)]=42
C. 2[2033(上)/1023(下)]=28
D. 2[3143(上)/3143(下)]=44
E. 2[3133(上)/3133(下)]=40