单项选择题
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
A.150h B.180h C.190h D.160h
A.60 B.70 C.80 D.90
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