Which nerve innervates the skin at the level of the symphysis pubis over the genital area?

The correct choice is L1. The L1 nerve is part of the lumbar plexus and innervates the skin in areas associated with the lower abdominal wall and the upper groin region, including the area over the symphysis pubis. Specifically, the skin over the genital area, particularly in males and females, receives sensory input from branches of the L1 nerve, which contributes to the iliohypogastric and ilioinguinal nerves.

While other nerve roots are involved in innervating different regions of the body, they do not provide primary sensory innervation at the level of the symphysis pubis. T12 generally contributes to innervation of the lower abdomen but does not specifically target the genital area as directly as L1. S1, part of the sacral plexus, primarily innervates areas further down the lower limbs and pelvis rather than the specific skin overlaying the symphysis pubis. T6 is associated with the upper abdominal wall and is not related to the genital area either.

Thus, the L1 segment is the most relevant in this context for providing sensory innervation to the skin over the genital area at the level of the symphysis pubis.