Onye otu ọkpọkọ na-ejikọta ọkpọkọ nke nwere mgbidi nwere nnukwu ogwe aka nwere eriri aka nwere ụdị arc, nke e ji mara n'ihi na enwere njikọ kwụwara n'etiti n'ikpere ụkwụ gbagọrọ agbagọ. A na-eji ígwè nkedo, igwe anaghị agba nchara, alloy ígwè, ihe nkedo calcinable, carbon ígwè, meta ndị na-abụghị ígwè...
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