**Core Concept**
The carpal tunnel is a narrow anatomical passage in the wrist that contains the median nerve and several flexor tendons. The median nerve is responsible for innervating the muscles of the thenar eminence and providing sensation to the palmar surface of the thumb, index, middle finger, and the radial half of the ring finger.

**Why the Correct Answer is Right**
The ulnar nerve, on the other hand, is a separate nerve that passes through the Guyon's canal, which is located on the ulnar (medial) side of the wrist. The ulnar nerve is responsible for innervating the muscles of the hypothenar eminence and providing sensation to the palmar surface of the little finger and the ulnar half of the ring finger. Therefore, the ulnar nerve is not contained within the carpal tunnel.

**Why Each Wrong Option is Incorrect**
* **Option A:** Flexor pollicis longus is a flexor tendon that passes through the carpal tunnel, but it is not a nerve.
* **Option B:** Flexor digitorum profundus is a flexor tendon that also passes through the carpal tunnel, but it is not a nerve.
* **Option D:** Median nerve is indeed a content of the carpal tunnel, which is why option C is correct.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the median nerve is responsible for the thenar eminence muscles, while the ulnar nerve is responsible for the hypothenar eminence muscles. This distinction is crucial in diagnosing nerve injuries and compressions in the wrist.

**✓ Correct Answer:** C. Ulnar nerve