Txheej: 3 txheej.nws yog cov qauv sib xyaw ntawm cov hlau thiab yas, nws kov yeej qhov kev ntxhov siab nrawm nrawm ntawm cov kav dej yas.
Nws muaj rigidity thiab cuam tshuam tsis kam uas tshaj cov kav dej ntshiab zoo tib yam,