I and O Ir and O Fe and O Pb and O
I gave my students this multiple choice question: Iron oxides, such as rust, form when iron metal reacts with oxygen in the air. What are the chemical symbols for the two elements found in iron oxide?

Only one answer is correct among these 4 choices:
- I and O
- Ir and O
- Fe and O
- Pb and O

Could you tell me which one is correct?

Fe and O