Tig xa mus
Vim tias kev txwv tsis pub muaj kev sib koom tes los yog cov koomhaum ntawm cov khw muag khoom hauv cov khoom cog khoom tsis yog ib qho kev qhia tawm, muaj qee qhov arc, rectangular thiab s hom kab ncaj ncaj, tab sis txoj kev xa tsheb mus los yog ib qho, tonnage loj, yog cov nqi ntawm cov khoom siv rau kev saib xyuas, tig tsheb yog cov kev xaiv uas lawv pom.
