Fact 1: Chemical weathering causes iron in rock to oxidize.

Fact 2: Oxides Oxides Oxides are elements combined with oxygen.

Given the two facts above, answer the question "Chemical weathering causes iron in rock to combine with what?" with the following options: 
- uranium
 - oxygen
 - cartilage
 - nothing
 - an object
 - vacuum
 - energy
 - heat


 

  oxygen       