单项选择题
The boiling and condensation points of refrigerant mainly depend on the （） exerted upon it.
A.temperature B.density C.volume D.pressure
单项选择题 In a compression refrigeration plant the refrigerant is under low pressure in the （） and under high pressure in the （）.
单项选择题 A feeler or thermal bulb is used for the expansion valve to （）.
单项选择题 The expansion valve on a Freon system controls the （）.
