Which one of the followings might not be employed to create vacuum for flash type evaporator? （）

单项选择题The design of for a flash type evaporator is of critical importance because it must provide an optimum feedwater spray pattern that facilitates the flashing process, and it must also maintain a pressure differential between successive stages（）

A.condenser
B.flashing device
C.lashing device
D.vacuum pump

单项选择题A flash-type evaporator discharges heated seawater into a chamber that is maintained at a pressure than the vapor pressure of the entering heated seawater, and subsequently the flashed water vapor thereby produced（）

A.lower condensing
B.higher cooling
C.lower cooling
D.higher condensing

单项选择题Before the sludge in a purifier is ejected,（）

A.the oil feeding is stopped and replaced by admitting flushing water
B.the flushing water feeding is stopped and replaced by admitting oil
C.the feeding of dirty oil and flushing water is stopped
D.the feeding of dirty oil and flushing water is admitted

单项选择题A centrifuge of which the bowl is arranged as the upper and lower parts separate discharges the sludge（）

A.by opening the separator manually
B.by separating the lower part from the upper part automatically
C.by separating the upper part from the lower part automatically
D.continuously

单项选择题“A centrifuge consists of an electric motor driving a vertical shaft on the top of which is mounted the bowl assembly”.According to this sentence, we can know that is mounted on the top of the vertical shaft（）

A.a centrifuge
B.an electric motor
C.a bowl assembly
D.a driving motor