Tsim los ua ib feem tseem ceeb ntawm thaj chaw kev kawm hla kev, txaus siab thiab siv taus yog qhov tseem ceeb. Ob-theem high-peev cia system rau kev nkag tau yooj yim li gym xav tau nce. Ua tsaug rau DHZ cov khoom siv haib thiab ntau lawm, qauv qauv ntawm cov khoom siv ruaj khov thiab muaj tsib-xyoo lav.