Final answer:
The radial nerve innervates the posterior compartment of the forearm, responsible for extending the wrist and fingers, not the medial, lateral, or anterior compartments.
Step-by-step explanation:
The anatomy of the radial nerve includes the innervation of the posterior compartment of the forearm. Therefore, the correct answer to the question is d. Posterior forearm. The radial nerve is not responsible for the innervation of the medial forearm (a), the lateral forearm (b), or the anterior forearm (c). The muscle groups in the posterior compartment of the forearm are primarily responsible for extension of the wrist and fingers and are innervated by the radial nerve. This contrasts with the anterior compartment of the forearm, where muscles, which arise from the medial epicondyle of the humerus, flex the wrist and fingers and have a different nerve supply.
The forearm flexors, such as the biceps brachii, brachialis, and brachioradialis, are located in the anterior compartment of the arm and are not innervated by the radial nerve. Instead, these muscles are predominantly innervated by the musculocutaneous nerve. The posterior compartment of the forearm, where the radial nerve operates, contains muscles such as the extensors of the wrist and fingers.