You are presented with the question "What causes iron to rust?" and the following answer choices: 
- Chemical energy
 - High pressure
 - harmful substances
 - Greenhouse gasses
 - permineralization
 - Chemical weathering
 - Cold temperatures
 - Direct heat

Now knowing that chemical weathering causes iron in rock to oxidize and when iron oxidizes, it rusts, choose the best answer.


 

      Chemical weathering   