Yas zaj duab xis raws li cov khoom siv luam ntawv, nws yog luam tawm raws li lub hnab ntim khoom, nrog lub teeb thiab pob tshab, ya raws thiab oxygen tsis kam, huab cua zoo nruj, tawv thiab folding tsis kam, du nto, tuaj yeem tiv thaiv cov khoom, thiab tuaj yeem tsim cov duab zoo nkauj. ...
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