单选题Which of the valves listed is NOT considered to be a hydraulic system directional control valve?（）ASpring-centered valveBUnloading valveCThree-position valveDTwo-position valve
单选题
Which of the valves listed is NOT considered to be a hydraulic system directional control valve?（）
A
Spring-centered valve
B
Unloading valve
C
Three-position valve
D
Two-position valve
参考解析
解析：
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