Cov txheej txheem ntawm kev tsim cov txheej saum npoo av nyob rau saum npoo ntawm cov khoom siv txheej txheem ntawm cov txheej txheem ntawm cov khoom siv, thiab cov yam ntxwv siv lub cev, thiab tshuaj lom neeg yog lub npe hu ua kev kho deg.
Nyeem ntxiv