@AutonomousTacticalTheory why do you think this was if you dont mind my asking

Can someone clarify an issue I had with answer choice C: I thought this was a trap choice because while the passage mentions that "all known asteroids contain iron" it never says if these asteroids are in our solar system or not. Is this mentioned somewhere else that I missed or am I just supposed to assume that because we know about them that they must not be outside our solar system?