Gene's parachute did not open when he jumped out of the airplane. He injured his back in the thoracic and lumbar regions, damaging the autonomic ganglia found close to his spinal cord. What neurons did he likely damage?

sympathetic preganglionic neurons

Explanation:

Sympathetic preganglionic neurons  are present in close proximity to the spinal cord and are located within the CNS. The origination starts from 12 thoracic and first 2-3 lumbar segments of the spinal cord.

Therefore if Gene injured his back in the thoracic and lumber region than sympathetic preganglionic neurons are the neuron that must be damaged in his body. Sympathetic preganglionic neurons are shorter than parasympathetic preganglionic fibers as they are present in proximity to the spinal cord. So the correct answer is sympathetic preganglionic neurons.