Ameslikas tsim raws li kev txhawb nqa ntawm cov ntawv txheej hauv cov khoom ntim, scrim tau ua pov thawj tias yog cov khoom siv ntau yam nrog ntau hom kev cai.Nws yog cov khoom siv zoo rau kev txhawb nqa ntau yam khoom lag luam xws li vov tsev, ntaub pua plag, cua-ducts, lim, daim kab xev, laminations, thiab lis ...
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