**Core Concept**
The question is testing the student's knowledge of the innervation and supply of various muscles in the upper limb. The median nerve is a major nerve that supplies muscles and sensation to the anterior aspect of the arm, forearm, and hand. However, it does not supply all muscles in the upper limb.

**Why the Correct Answer is Right**
The correct answer is a muscle that is supplied by a different nerve. The infraspinatus muscle is a rotator cuff muscle located in the shoulder region, and it is primarily supplied by the suprascapular nerve, not the median nerve. The suprascapular nerve arises from the superior trunk of the brachial plexus and innervates the infraspinatus and teres minor muscles.

**Why Each Wrong Option is Incorrect**
* **Option A:** The flexor carpi radialis muscle is actually supplied by the median nerve, not another nerve.
* **Option B:** The biceps brachii muscle is also supplied by the median nerve, making it an incorrect option.
* **Option D:** The trapezius muscle is supplied by the accessory nerve (cranial nerve XI), but it's not the correct answer as the question specifically asks for a muscle not supplied solely by the median nerve.

**Clinical Pearl / High-Yield Fact**
The suprascapular nerve is a branch of the brachial plexus that arises from the superior trunk and supplies the infraspinatus and teres minor muscles. This nerve is often injured in shoulder surgeries or sports-related injuries, leading to weakness of these muscles.

**Correct Answer: C. Infraspinatus**