Which nerve innervates the subclavius?

The subclavius muscle is primarily innervated by the nerve to the subclavius. This specific nerve originates from the upper trunk of the brachial plexus and provides the necessary motor innervation to the subclavius, enabling it to perform its function of stabilizing the clavicle and assisting with movements of the shoulder girdle.

The other options, while mentioning potential nerves, do not directly supply the subclavius. The median nerve primarily innervates muscles of the forearm and hand, the scapular nerve pertains to muscles involving the scapula, and the musculocutaneous nerve primarily innervates muscles in the anterior compartment of the arm. Thus, the nerve to the subclavius is clearly the correct choice as it directly correlates with the known anatomy and function of the muscle in question.