单项选择题
A.0.1~0.5mm B.0.6~1.0mm C.1.O~1.5mm D.1.5~2.0mm
A.20% B.30% C.10% D.15%
A.253V B.242V C.220V D.380V
A.0.5m/s B.1m/s C.1.5m/s D.1.5m/s
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