单项选择题
Which of the following pumps is most suitable for an oily water separator?（）
A.reciprocating pump B.vane pump C.mono pump D.axial-flow pump
单项选择题 With reference to a two ram actuating mechanism, which one of the following statement is false?（）
单项选择题 The DC excitation to the field of brushless synchronous is generally produced by （）
单项选择题 Which of the following equipment is not pollution prevention equipment?（）
