单项选择题
A compound gage is used to measure （）.
A.temperature and pressure B.humidity and temperature C.pressure and vacuum D.pressure and humidity
单项选择题 A centrifugal pump attempting to develop flow against a closed discharge valve has a/an （）.
单项选择题 Condensate formed within the first-effect tube nest of a double-effect,low pressure evaporator, is removed by a （）.
单项选择题 The temperature of a refrigerant gas is the highest （）.
