单项选择题
A.lack of refrigerant
B.refrigerant with much water
C.set defectively low pressure relay
D.no cooling water
单项选择题 On modern ships, centrifugal pump with a self-primer has replaced reciprocating pump as bilge pump because（）
单项选择题 When a sudden increase in steam demand occurs from the boiler, the water level in the drum at the higher pressure will（）
单项选择题 Continuous surging of turbocharger can be caused by（） ①crash stop of engine ②increased back pressure after T-Ch ③fouled or damaged turbine nozzle ring