I. Cov Khoom Tseem Ceeb ntawm Cov Khoom Siv Yas 1. AS: Lub hardness tsis siab, kuj nkig (muaj lub suab nrov thaum tapping), pob tshab xim, thiab xim tom qab yog xiav, nws tuaj yeem ncaj qha rau hauv cov tshuaj pleev ib ce thiab zaub mov. Nyob rau hauv cov tshuaj pleev ib ce fwj thiab lub tshuab nqus tsev vacuum, nws yog peb ...
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