题目选项分析

In contrast to large steel plants that take iron ore through all the steps needed to produce several different kinds of steel,processing steel scrap into a specialized group of products has enabled small mills to put capital into new technology and remain economically viable.

In contrast to large steel plants that take iron ore through all the steps needed to produce several different kinds of steel,small mills, by processing steel scrap into a specialized group of products, have been able to put capital into new technology and remain economically viable.