单项选择题
The （）is not a component of an oil separator.
A.sliding bowl bottom B.gravity disc C.separating disc D.scum valve
单项选择题 The （）pump is usually used as the lubricating oil pump.
单项选择题 The reciprocating pump can’t draw water from a tank may be caused by （）.
单项选择题 （）sometimes called filter, is a device designed to prevent the passage of unwanted solids into the system.
