A.0.3~0.5MPa B.0.4~0.6MPa C.0.5~0.7MPa D.0.7~0.9MPa
A.暢通、清潔 B.不得互相纏繞 C.要有防磨措施 D.上述三項
A.60m B.72m C.84m D.100m