单项选择题
A.45°~60° B.30° C.30°〜45° D.55°〜60°
A.15mm B.10mm C.5mm D.20mm
A.1.5mm/m B.l.0mm/m C.0.5mm/m D.2.0mm/m
A.0.5mm B.1.5mm C.2.0mm D.3.5mm
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