[ Katniss doesn't laugh or sneer, but she doesn't look enthusiastic, either. While she hasn't had a lot of experience with the common car, she knows the concept, and it seems like it might need more than just what can be found in a TV. So she's skeptical, to say the least. ]

A car...

[ She doesn't doubt that he knows how to make one, though. She wouldn't like it if someone doubted her ability to bring down a bird with her bow and arrow. ]

That could be useful. You'll need more than just a TV though. And you shouldn't take apart all the TVs in case there's an announcement.