Cov txheej txheem ntxhov siab yog ib kauj ruam tseem ceeb hauv pob tw vuam, ua lub luag haujlwm tseem ceeb hauv kev tsim cov welds muaj zog thiab txhim khu kev qha. Kab lus no muab cov ntsiab lus ntawm cov txheej txheem ntxhov siab hauv pob tw vuam, nthuav dav nws qhov tseem ceeb, cov txheej txheem, thiab cuam tshuam rau qhov zoo ntawm vuam. Qhov tseem ceeb ntawm kev ntxhov siab: Kev ...
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