Cov ntsia hlau, tseem hu ua cement steel rau tes thiab cement steel rau tes, yog ib yam tshiab ntawm cov khoom siv. Nws yog ib hom tshiab ntawm cov khoom siv hauv tsev tsim los ntawm kev siv cov pob zeb tshwj xeeb. Nws yog ib yam khoom tshiab hauv kev tsim kho kev lag luam, feem ntau siv hauv kev tsim vaj tsev, hauv pob zeb ...
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