单项选择题
A.the four-way control valve failing to shift
B.the bleeder valve sticking in the open position
C.cold hydraulic fluid
D.a clogged air vent falter on the oil reservoir
单项选择题 If you are given the job of adding hydraulic fluid to a mooring winch, and are not certain as to the type of fluid to use, you should （）.
单项选择题 The output volume of a positive fixed displacement pump can be changed only by （）.
单项选择题 An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.