You are presented with the question "what between objects formed deep within the Earth causes them to smooth" and the following answer choices: 
- Movement
 - loose soil
 - erosion
 - contact
 - soils
 - break off
 - friction
 - Bend

Now knowing that contact between rocks over long periods of time causes rocks to smooth and metamorphic rocks are rocks formed by the alteration of preexisting rocks deep within the Earth, choose the best answer.


 

    contact     