单项选择题
Hydraulic control check value is generally used to （） in the marine hydraulic mechanism.
A.control the back pressure of return oil B.lock the oil lines under some conditions C.change the direction of oil flow D.act as relief valve
单项选择题 Check value is used to control （）
单项选择题 （）can cause oil flow from sludge outlet of self cleaning separator.
单项选择题 （）can not cause oil flow from water outlet of self-cleaning separator.
