I have learned that clothes online are of poor quality.A. boughtB. buyingC. to buyD. havi

问题补充：

I have learned that clothes online are of poor quality.

A. bought

B. buying

C. to buy

D. having bought

答案：

(答案→)A. bought

B. buying

C. to buy

D. having bought

解析：句意：我已经知道网上买的衣服质量差。这里需要定语修饰clothes，因为clothes和buy是被动关系，用过去分词做定语，所以选A.