Which of the following is not a possible cause of erosion? a. burrowing animals b. gravity c. water d. none of the above

The correct option as to which is not a possible cause of erosion is none of the above. As a matter of fact, all of these options can cause erosion one way or another. Burrowing animals dig into the ground, and thus can cause chunks of earth to fall apart and cause erosion. Gravity and water can do the same thing, so none of these options are incapable of causing erosion, that is, all of them can do it.