that is what friends are for

问题描述:

that is what friends are for
请分析下语法,

这就是朋友所代表的意义.
That is引导的是主语从句,that是逻辑主语,普通语序是What friends are for is that.也就是说“what friends are for”是真正的主语.但太长了.所以英语习惯上用That引导的主语从句表达