He was very rude to the Customs officer of course made things even worse.A. whoB. whomC.

问题补充：

He was very rude to the Customs officer, of course made things even worse.

A. who

B. whom

C. that

D. which

答案：

A. who

B. whom

C. that

(答案→)D. which

解析：考查定语从句本句引导词指代前文整句话，做介词of宾语，故只能使用which。选D。