单项选择题
A.1mm B.2mm C.3mm D.4mm
A.0.3mm B.0.4mm C.0.5mm D.0.6mm
A.1/3 B.1/4 C.1/2 D.3/5
A.可略低于 B.应高于 C.不得低于 D.可略高于
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