You are presented with the question "What breaks rocks down?" and the following answer choices: 
- In the winter
 - Calcium carbonate
 - an engine
 - the Great Barrier Reef
 - mechanical force
 - permineralization
 - at or near the margins
 - mechanical

Now knowing that weathering means breaking down rocks from larger whole into smaller pieces by weather and water is a mechanical weathering force, choose the best answer.


 

     mechanical force    