【正确答案】 C

【答案解析】[解析] than后的从句的主语若是主句中提到的名词，谓语是动词be时，可以省略从句的主语，有时be也略而不用。此句实际上是省略了主语they (the dictionaries)，如《大学英语》精读第四册第七课The Luncheon中有这样一句话：She gave me the impression of having more teeth, white and large and even, than were necessary for any practical purpose.又如：There were more casualties than was reported(=than it was reported there were).