Cov roj tseem ceeb ntawm txiv kab ntxwv qab zib yog ib qho ntawm ob peb cov roj tseem ceeb uas muaj cov nyhuv so kom txaus. Nrog rau cov ntxhiab tsw qab ntawm txiv kab ntxwv qab zib, nws tuaj yeem tshem tawm kev ntxhov siab thiab kev ntxhov siab, txhim kho kev pw tsaug zog tsis taus uas tshwm sim los ntawm kev ntxhov siab, ua rau tawm hws, thiab yog li pab tshem tawm cov tshuaj lom ntawm daim tawv nqaij uas raug txhaws. Nws pab tau rau cov tawv nqaij uas rog, tawv nqaij pob txuv lossis tawv nqaij qhuav.