The factory produces half a million pairs of shoes every year 80% are sold abroad.A. of t

问题补充：

The factory produces half a million pairs of shoes every year,80% are sold abroad.

A. of them

B. which of

C. of which

D. of that

答案：

A. of them

B. which of

(答案→)C. of which

D. of that

解析：

试题分析:考查定语从句。由结构判断后面是非限制性定语从句，排除A、D选项，而B选项形式错误，故答案选C。句意：这家工厂每年生产五十万双鞋，其中80%都被销售到了国外。