Nrog rau kev txhim kho txuas ntxiv ntawm lub zog tshiab tsheb, cov roj teeb hluav taws xob kuj tau txais kev saib xyuas ntau dua.Roj teeb, lub cev muaj zog thiab hluav taws xob tswj qhov system yog peb lub hauv paus tseem ceeb ntawm lub zog tshiab tsheb, ntawm cov roj teeb lub zog yog qhov tseem ceeb tshaj plaws, tuaj yeem hais tias yog "nws ...
Nyeem ntxiv