**Core Concept**
The anterior interosseous nerve is a branch of the median nerve that supplies muscles in the forearm responsible for thumb and finger movements. It primarily targets flexor muscles of the forearm.

**Why the Correct Answer is Right**
The anterior interosseous nerve innervates the flexor pollicis longus, pronator quadratus, and the lateral half of the flexor digitorum profundus in the forearm. These muscles are key to thumb and finger flexion, and their innervation is unique to the anterior interosseous nerve. The nerve's course and branching explain why it targets these specific muscles.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the anterior interosseous nerve does not supply the flexor carpi radialis, which is actually innervated by the median nerve but through a different branch.
**Option B:** This option is incorrect because the anterior interosseous nerve does not supply the flexor digitorum superficialis, which is innervated by the median nerve through the anterior interosseous nerve's parent nerve, but not directly by the anterior interosseous nerve itself.
**Option C:** This option is incorrect because the anterior interosseous nerve does not supply the palmaris longus, which is actually innervated by the median nerve but through a different branch.
**Option D:** This option is incorrect because the anterior interosseous nerve does not supply the flexor carpi ulnaris, which is actually innervated by the ulnar nerve.

**Clinical Pearl / High-Yield Fact**
Remember that the anterior interosseous nerve is a branch of the median nerve that supplies flexor muscles in the forearm involved in thumb and finger flexion. Be aware of its distinct branching pattern to avoid confusion with other branches of the median nerve.

**Correct Answer:** C. palmaris longus.