单项选择题
A.60° B.55° C.30° D.40°
A.60° B.30° C.55° D.40°
A.干切削 B.水溶性切削液 C.非水溶性切削液 D.任意
A.中间1/3 B.上面/3 C.下面1/3 D.1/3
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