The factory produces two million pairs of shoes every year half are sold abroad.A. of w

问题补充：

The factory produces two million pairs of shoes every year, half are sold abroad.

A. of which

B. which of

C. of them

D. of that

答案：

(答案→)A. of which

B. which of

C. of them

D. of that

解析：本题考查定语从句。“逗号”不能连接两个句子，所以所选之词应是连词，排除C项；that不能引导非限制性定语从句，排除D；介词应用在of前。