单项选择题
Check value is used to control （）
A.direction of oil flow B.back pressure of return oil C.bypass of filter D.high pressure overflow
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.
单项选择题 （）can cause oil flow from water outlet of a separator.
