In class, the teacher brought a piece of ore for A, B, C 3 students to identify  It's not iron, it's not lead,  A said  It's not iron, it's copper,  B said  It's not copper, it's iron, C said  The teacher concluded: Of the three, one person's two judgments are correct
The other person's two judgments are wrong, and one person's two judgments one-on-one wrong
This ore is lead