正常情况下左反推由哪个液压系统供压()
A液压系统
B液压系统
C. 备用液压系统
D. 地面液压源
A gas-free certificate would usually be issued by a(n)().
ABS marine surveyor
B. certified marine chemist
C. port engineer
D. Coast Guard marine inspector
C620-1车床上加工螺纹,丝杆螺距为12mm,车削螺距为()mm螺纹不会产生乱扣。
A. 1.25
B. 1.75
C. 2
D. 2.5