请问这句话为什么要加that

问题描述:

请问这句话为什么要加that
His dream is that he can go to a key school .

当然要that啊,is个谓语,后面只能接宾语,that是引导一个从句,解释dream的内容的,充当is的宾语,也就是that引导宾语从句