A.銅、鉛、鋅 B.銅、鈷、銀 C.銅、錳、鉻 D.銅、鋅、鉬
A.棕剛玉 B.黑碳化硅 C.白剛玉 D.碳化硼
A.0.01~0.1㎜ B.0.1~0.25㎜ C.0.2~0.3㎜ D.0.3~0.35mm