Umoya onamandla wokuvikelwa kwemvelo, njengokuvinjelwa kokukhiqizwa ngenkathi yokushisisa, wahlukumeza kakhulu izimboni eziningi ezifana nensimbi, imboni yamakhemikhali, usimende, i-electrolytic aluminium, njll. Abangaphakathi embonini bakholelwa ukuthi ukuphela konyaka imakethe yensimbi izoba esinye isiyaluyalu, amanani. noma...
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