Cia peb saib qhov kev zoo nkauj ntawm cov ntsiab lus ntawm 6-sided laum tshuab, lub rooj txav tau muab kev txhawb nqa muaj zog, ob chav rail sab kev sib raug zoo yog qhov tseeb, qhov kev teeb tsa ntawm lub txhab nyiaj drilling yog tsim nyog nrog kev ua haujlwm siab. Ob chav drilling bank, ob chav ua haujlwm cheeb tsam, pom qhov tsis pom, sab ...
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