单项选择题
A.1050mm B.1100mm C.1200mm
A.1000mmB.1050mmC.1100mm
A.35≤Φ(直径)≤55mm B.30≤Φ(直径)≤50mm C.25≤Φ(直径)≤45mm
A.≤4m,7m B.≤5m,6m C.≤6m,5m
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