You are presented with the quiz "What was formed through erosion over long periods of time?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "most canyons are formed by flowing rivers through erosion over long periods of time" and "the Columbia River Gorge is a spectacular river canyon cutting through the volcanic rock of the Cascade Mountain Range". 

So, what's the best answer to the question?


 

 Columbia River Gorge          