The Granite Boulders in Rocky Mountain National Park Are a Favored

The granite boulders in Rocky Mountain National Park are a favored place among talented climbers who specialize in the art of bouldering, or climbing harder (but shorter) routes without tying into a rope. Climbers have taken to (illegally) stashing foam crash pads underneath the boulders but marmots and other rodents chew up the pads and the litter is spread by the wind. Why would the park be overused in this manner?

A) Because the marginal private benefit of using the park is greater than the marginal social benefit of using the park
B) Because the marginal social benefit of using the park is greater than the marginal private benefit of using the park
C) Because there are no external costs to using the park
D) Because the marginal private cost of using the park is less than the marginal social cost of using the park