Hlau tsis yog tsuas yog rau kev sib kis ntawm cov kua dej thiab cov hmoov av, kev sib hloov hluav taws xob, kev tsim khoom ntawm cov khoom siv thiab cov ntim khoom, nws yog cov khoom siv nyiaj txiag. Lub tsev tsim nrog cov yeeb nkab steel tsim daim phiaj, ncej thiab kev txhawb nqa tshuab, tuaj yeem txo qhov hnyav thiab txuag 20 mus rau 40% hlau, thiab tuaj yeem ...
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