单项选择题
A.低速 B.中速 C.高速 D.空
A.1/4 B.1/2 C.3/4 D.5/8
A.10~15L/mm B.12~18L/mm C.15~20L/mm D.18~23L/mm
A.4mm~6mm B.6mm~8mm C.8mm~10mm D.10mm~12mm
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