You are presented with the question "what smooths over long periods of time due to contact?" and the following answer choices: 
- h2o
 - alluvial
 - granite
 - calcite
 - loose soil
 - soil
 - mountains
 - erosion

Now knowing that contact between rocks over long periods of time causes rocks to smooth and granite is a common rock in continents, choose the best answer.


 

   granite      