单项选择题
A.whenever B.however C.wherever D.whether
Gear pumps are （） because they discharge a near constan...
单项选择题Gear pumps are （） because they discharge a near constant amount of liquid regardless of pressure.
A.negative displacement type B.turbine type C.positive displacement type D.mixed-flow type
Keep compartment （） as the gas given off can be dangero...
单项选择题Keep compartment （） as the gas given off can be dangerous.
A.well ventilated B.well clean C.in good order D.more room
More than one stage of evaporation can take place by ad...
单项选择题More than one stage of evaporation can take place by admitting the sea water into chambers with progressively （） pressure in the flash evaporator.
A.lower B.higher C.the lower D.the higher
