?8391.(1) Relief valves are used in pneumatic systems as damage-preventing units.(2) Check valves are used in both hydraulic and pneumatic systems.Regarding the above statements,
发布于 2021-02-18 22:09:12
【单选题】 A ?both No.1 and No.2 are true. B ?neither No.1 nor No.2 is true. C ?only No.1 is true.
