单项选择题
A.Relief valves
B.Check valves
C.Safety valves
D.Reducing valve
单项选择题 Among the basic categories of equipment, which of the following is used to convert hydraulic energy into continuous rotary motion?（）
单项选择题 Among the basic categories of equipment, which of the following are used to convert mechanical into hydraulic energy?（）
单项选择题 The drive motor will have a brake arranged to fail-safe, i√eit will （） the load if power fails or machine is stopped.