Why aren't small asteroids spherical in shape?

A) The strength of gravity on small asteroids is less than the strength of the rock.

B) Small asteroids have odd shapes because they were all chipped off larger objects.

C) Large asteroids were once molten and therefore became spherical, but small asteroids were never molten.

D) Large asteroids became spherical because many small collisions chipped off pieces until only a sphere was left; this did not occur with small asteroids.