题目解析:
C以modern buildings做关键词定位至最后一句的buildings built now: Progress in this area can be measured by the difference in weight between buildings built now and those of comparable size built one hundred years ago.说比较现在和一百年前大小相似的建筑的重量我们就能发现建筑技术所取得的进步,也就是以前的重现在的轻,所以答案是C,其他的都没说。