1. Roob tsheb kauj vab kev txawj ntse 1: cov khoom siv thav duab Cov ntaub ntawv tseem ceeb ntawm cov ncej yog steel ncej, aluminium alloy thav duab, carbon fiber thav duab, thiab nano-carbon thav duab.Ntawm lawv, qhov hnyav ntawm steel ncej tsis yog lub teeb.xeb, thev naus laus zis tau raug tshem tawm, tab sis ...
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