题目解析:
定位第4段简化句,分析:industrialization of book production proceeded more rapidly in the United States,原因有二(1)larger than in Britain ,(2)more sensitive to price than to quality,后面because elite readers constituted a smaller proportion of book buyers作为(2)的原因。
选项A的were similar inquality,选项B的than is usually realized,选项D的not as sensitive to quality as均未提及,错误;
选项C符合原文主干及原因(1)(2)。
故选C