**Core Concept**
The median nerve is a mixed nerve that supplies both motor and sensory functions to the hand. A lesion at the wrist can result in a range of clinical manifestations due to the involvement of these functions.

**Why the Correct Answer is Right**
A lesion of the median nerve at the wrist can cause thenar atrophy due to the involvement of the motor branches that innervate the thenar muscles (thumb muscles). It can also cause numbness and paresthesia in the palmar surface of the thumb, index, middle finger, and the lateral half of the ring finger due to the involvement of the sensory branches. Furthermore, the median nerve supplies the muscles of the anterior forearm, including the pronator teres, which can lead to weakness in forearm pronation.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not directly related to median nerve function. The median nerve does not supply the flexor pollicis longus muscle, which is actually innervated by the anterior interosseous branch of the median nerve, but the flexor pollicis longus is primarily responsible for thumb flexion at the interphalangeal joint, not the median nerve's primary function.
**Option B:** This option is incorrect because the median nerve does not supply the flexor carpi radialis muscle. The flexor carpi radialis is a forearm muscle involved in wrist flexion and radial deviation and is actually innervated by the radial nerve.
**Option C:** This option is incorrect because the median nerve does not supply the extensor digitorum muscle. The extensor digitorum is a forearm muscle involved in finger extension and is actually innervated by the posterior interosseous branch of the radial nerve.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the median nerve supplies the thenar muscles, which are responsible for thumb opposition, and that a lesion at the wrist can lead to thenar atrophy and weakness in thumb function.

**Correct Answer: D.**