坐骨神经痛最常见的病因是() ["马尾肿物","腰椎间盘突出","坐骨神经外伤","腰骶椎炎","腰骶神经根炎"]
煤粉的输送和流化性质主要由()决定。 ["煤粉的灰分含量","煤粉的粒径分布","煤粉的温度","煤粉的含水量"]
光缆中断时朗讯光传输设备一定会亮的告警灯是() ["A、PROMPT","B、INFO","C、DEFAULT","D、对应的Rx"]
什么叫破断强度?
螺杆式制冷压缩机机体两端设有成()的吸、排气孔口,通过转子旋转运动达到吸气、压缩和排气目的 ["对角线布置","平行布置","直角布置","交错布置"]
链条的容许拉力怎样计算?