You are presented with the question "Rust of iron in rocks is a direct result of " and the following answer choices: 
- solar heating
 - high speed fall from space
 - Chemical energy
 - The area was once underwater
 - permineralization
 - Temperature
 - volcanic ejection
 - chemical weathering

Now knowing that chemical weathering causes iron in rock to oxidize and when iron oxidizes it produces iron oxide, more commonly referred to as rust, choose the best answer.


 

        chemical weathering 