单项选择题
A.0.5mm B.1.5mm C.2.5mm D.3.5mm
A.30° B.40° C.50° D.60°
A.Ф37mm B.Φ38.5mm C.Φ39mm D.Φ39.5mm
A.15% B.20% C.25% D.30%
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