Low compression pressure in a diesel engine may be the result of ()
A. insufficient fuel supply due to fuel pump valves sticking or leaking
B. excessive mechanical clearance between the piston crown and cylinder head
C. excessively worn fuel pump plunger
D. excessive exhaust back pressure
井下两机车或两列车在同一轨道的同一方向行驶时,必须保持不少于()的距离。
A. 50m
B. 100m
C. 150m
D. 200m
部分钠离子交换法中,最终是利用()去软化未经钠离子交换器的生水的硬度的。
A. NaHCO3
B. NaOH
C. Na2CO3
D. NaCL
JWK型经济型数控机床系统通电后,如长时间不运行,应将功放开关置于()位置。
A. 接通
B. 断开
C. 手动
D. 选择