Txhua tus dev yog ib qho txuj ci tseem ceeb ntawm qhov xwm txheej. Lawv yog cov ncaj ncees, siab zoo, thiab qab zib tshaj plaws. Qhov no yog khoom plig rau tib neeg.
Kev sib xyaw ntawm cov dev ntawm cov tsiaj sib txawv yog ib qho txuj ci tshwj xeeb. Lawv tau txais qhov zoo tshaj plaws los ntawm ob hom.
Tsuas yog ua tib zoo saib cov kev sib xyaw ntxim hlub no.