单项选择题
A.cool the expansion valve
B.prevent refrigerant superheating
C.condense the refrigerant gas
D.prevent motor overheating
单项选择题 Which of the listed operations will cause an automatically controlled refrigeration compressor to restart?（）
单项选择题 In an electro-hydraulic steering gear system, when will the variable displacement pump be placed on stroke?（）
单项选择题 An additive used to improve the ability of a lube oil to reduce friction is known as a/an （）.