单项选择题
A.5mm B.10mm C.15mm D.20mm
A.0.025~O.05mm B.0.25~0、5mm C.0.25mm左右 D.0.5mm左右
A.l周 B.40周 C.1/40周 D.1/2周
A.15mm B.20mm C.25mm D.30mm
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