单项选择题
A.30° B.45° C.60° D.90°
A.0.002 B.0.003 C.≤0.001 D.≤0.01
A.≤0.001 B.≤0.01 C.≤0.005 D.≤0.002
A.中凹形状 B.中凸状 C.凹凸不平状 D.任意形状
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