单项选择题
While troubleshooting a refrigeration system for low head pressure, liquid refrigerant flooding back from the evaporator is determined to be the causeIt may be necessary to （）.
A.change the expansion valve adjustment B.readjust the water regulating valve to increase the flow of water C.purge air from the condenser D.clean the waterside of the condenser
单项选择题 Air trapped in the hydraulic fluid of a steering system should be indicated by （）.
单项选择题 Overgreasing of ball bearings installed on pumps will result in （）.
单项选择题 The energy associated with molecules is known as （）.
