Taobao.com is a free site, ________ visitors can not just buy almost all kinds of products but open their own online shops．

A.whose

B.which

C.what

D.where

答案及解析： D

解析：

考查定语从句中引导词的判断。定语从句中缺少地点状语，故用where引导，修饰free site。