单项选择题
A.铜、铅、锌 B.铜、钴、银 C.铜、锰、铬 D.铜、锌、钼
A.棕刚玉 B.黑碳化硅 C.白刚玉 D.碳化硼
A.0.01~0.1㎜ B.0.1~0.25㎜ C.0.2~0.3㎜ D.0.3~0.35mm
A.40~70min B.50~80min C.60~90min D.30~60min
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