PREVIOUSLY THE POOR QUALITY OF THE IRON HAD RESTRICTED ITSUSE IN ARCHITECTURE TO ITEMS SUCH AS CHAINS AND TIE BARS FOR SUPPORTING ARCHES, VAULTS, ANDWALLS

57. Đáp án là D: Ý trong bài: Previously the poor quality of the iron had restricted its

use in architecture to items such as chains and tie bars for supporting arches, vaults, and

walls. With the improvement in refining ore, it was now possible to make cast-iron

beams, columns, and girders.