He is a boy who is good at maths who is good at maths是定语从句 那里面的主谓宾是什么吖
问题描述：
He is a boy who is good at maths who is good at maths是定语从句 那里面的主谓宾是什么吖
答
He（主语） is （系动词）a boy who is good at maths who is good at maths（表语）
在表语中有一个定语从句who is good at maths ,修饰a boy.