my mother looks so young,that you would think her my sister.so young是什么语?（宾语或补语?）

题目

my mother looks so young,that you would think her my sister.so young是什么语?（宾语或补语?）
that you would think her my sister是从句吗?什么从句?

答案

so young是表语,这里的looks看起来的意思,相当于系动词,构成系表结构.
that后面的是从句,是和前面的so构成的so.that...结果状语从句.