Explanation

The primary energy conversion upon penetration is into heat and sound/deformation work. Option A is incorrect because potential energy relates to position or state, not the immediate loss of kinetic energy during impact. Option C includes 'Both B&D', but since D (Mechanical energy) is generally conserved unless work is done against non-conservative forces, it's less accurate than just heat. Option D is incorrect because mechanical energy is what is being converted away from its initial form.