单项选择题
A.0.7 B.0.4 C.0.9 D.0.8
A.4/100 B.5/1000 C.2/1000 D.3/1000
A.调速阀 B.溢流阀 C.单向阀 D.换向阀
A.三曲拐 B.二曲拐 C.六曲拐 D.直轴
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