Ivory board feem ntau yog siv los ntim cov khoom lag luam siab, xws li cov thawv tshuaj, lub thawv luam yeeb, thawv tshuaj pleev ib ce thiab lwm yam.Txawm li cas los xij, nrog kev kho dua tshiab thiab hloov pauv ntawm kev noj, daim ntawv thov ntau yam ntawm ivory board txuas ntxiv nthuav dav.Thaum sawv daws mus yuav khoom sab nraud thiab yuav...
Nyeem ntxiv