The American people will never forget the 9.11 event and the psychological trauma caused to hundreds of thousands of mon households.
A. that
B. it
C. which
D. what
网友回答
A. that
(答案→)B. it
C. which
D. what
解析：句意：美国人永远不会忘记9.11事件和它给成百上千的家庭带来的心灵创伤。it指代9.11事件，在定语从句中做主语；which和that都做定语从句的关系词，代替先行词做主语，the psychological trauma是先行词，在从句中做宾语，可以省略。what不是定语从句的关系词。 故选B。
考点: 考查代词的用法。