单项选择题
A.1.5mm B.2.0mm C.2.5mm D.3mm
A.15% B.20% C.10% D.30%
A.0.4m B.0.3m C.0.5m D.1m
A.1mm/m B.1.5mm/m C.2mm/m D.2.5mm/m
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