The answer to the question is B. How would marine animals make a huge canyon? I don't think marine animals were by or in this area at the time.
Erosion basically destroys rocks and soil by wind, water, etc. This would have some effect to making the canyon.
Deposition of Sediment means to move rocks and soil that erosion did. The Colorado River is basically inside of the Grand Canyon and then some.
So the only logical answer is B.
