一题语法请教各位

According to cognitive theories of emotion, anger occurs when individuals believe that they have been harmed and that the harm was either avoidable and undeserved.

A according to. B have been. C that the harm. D either.

正确答案 D.

问题:选项C为什么正确,that是否多余

believe that...and that..

两个并列的宾语从句