Final answer:
Axons running through large nerves, avoiding cartilage and skin, is NOT a step in motor axon growth to muscles. Motor axons follow a path to reach muscle fibers and form motor units involving ventral roots, plexuses, and peripheral nerves.
Step-by-step explanation:
The step that is NOT a part of motor axon growth through peripheral nerves to muscles is C. Axons run through large nerves, avoiding cartilage and skin. The other options listed are integral parts of the process. The ventral horn of the spinal cord generates lower motor neurons whose axons pass through the ventral nerve root (Formation of ventral root) and may travel through a network named a plexus before diverging into the peripheral nerves. Eventually, these axons reach their targeted muscle fibers and form a functional group known as a motor unit. However, motor axons do not specifically avoid cartilage and skin on their journey to the muscles.