Responses
Starting a rebellion maybe? Either he knows she's noble and able to change this system or he's trying to find people who would go against the nobles.
Could be that he knows who she really is and is testing her
And he knows that Cesar's sword has the royal crest, or something like that
Cuz that's a deep ass question to ask someone out of the blue..even if she answered it so what? If you believed that she is a commoner then what is she supposed to do about it?