You are presented with the question "Flowing water forms most canyons through erosion over what?" and the following answer choices: 
- movement of tectonic plates
 - dry streambeds
 - long periods of time
 - Physical weathering
 - Time and energy
 - short periods of time
 - massive damage
 - calving glaciers

Now knowing that most canyons are formed by flowing rivers through erosion over long periods of time and rivers and glaciers are made of water, choose the best answer.


 

   long periods of time      