Qhov cuam tshuam rau qhov nro
Cov kev taw qhia ntawm lub npoo nro yog tangent mus rau lub kua nto thiab txiav kom sib npaug rau txoj kab sib cais ntawm ib qho ntawm ob feem ntawm cov kua saum npoo. Qhov nplawm saum npoo tsuas yog cuam tshuam nrog xwm thiab ntsuas kub ntawm cov kua. Feem ntau, qhov siab dua qhov kub, qhov qis dua qhov ua rau lub nplaim tawg. Tsis tas li, impurities tseem yuav hloov qhov nro ntawm cov kua. Piv txwv li, dej huv muaj qhov tsis zoo saum npoo av, thaum lub teeb meem saum npoo ntawm dej xus npus yog qhov me me. Qhov ntawd yog hais, saum npoo ntawm cov dej huv muaj qhov ntau dua qub zuj zus.