单项选择题
A.阻力 B.压力 C.摩擦力 D.重力
A.12齿 B.14齿 C.16齿 D.18齿
A.0.5~2mm B.1~2mm C.1~2.5mm D.1~3mm
A.2mm B.2.5mm C.3mm D.3.5mm
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