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

问题补充：

The factory produces half a million pairs of shoes every year, 80% 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：此题考查定语从句。由于两句话之间无连词，所以只能构成定语从句；非限制性定语从句要用which指代物。