**Core Concept**
The question is testing the student's knowledge of dermatomal innervation, specifically the supply of the skin over the hypothenar eminence. The hypothenar eminence is a muscle group located on the palmar surface of the little finger, and the skin over this region is supplied by a specific branch of the ulnar nerve.

**Why the Correct Answer is Right**
The ulnar nerve is a branch of the medial cord of the brachial plexus, and it supplies the skin over the hypothenar eminence through its palmar cutaneous branch. This branch arises from the ulnar nerve in the forearm and provides sensory innervation to the skin over the hypothenar eminence. The palmar cutaneous branch of the ulnar nerve is responsible for transmitting sensory information from the skin over this region to the spinal cord.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the median nerve supplies the skin over the thenar eminence, not the hypothenar eminence.
* **Option B:** This option is incorrect because the radial nerve supplies the skin over the dorsal aspect of the hand, not the palmar aspect.
* **Option C:** This option is incorrect because the musculocutaneous nerve supplies the skin over the anterior aspect of the forearm, not the palmar surface of the hand.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the dermatomes of the ulnar nerve (C8-T1) correspond to the skin over the little finger and the hypothenar eminence. This knowledge is crucial in diagnosing nerve injuries or compressions that affect the ulnar nerve.

**Correct Answer:** C. Ulnar nerve.