单选题A more sophisticated pressure reducing valve incorporates a pilot valve which controls the fluid above the valve operating piston in response to downstream pressureThe bold and italic word “which” means （）.Aa pressure reducing valveBa pilot valveCan operating pistonDdownstream pressure
单选题
A more sophisticated pressure reducing valve incorporates a pilot valve which controls the fluid above the valve operating piston in response to downstream pressureThe bold and italic word “which” means （）.
A
a pressure reducing valve
B
a pilot valve
C
an operating piston
D
downstream pressure
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