**Core Concept**
The question likely refers to a medication-induced skin rash, specifically a condition known as **Fixed Drug Eruption (FDE)**. FDE is a type of skin reaction characterized by the formation of well-defined, circular or oval-shaped lesions that recur at the same sites after re-exposure to the offending medication.

**Why the Correct Answer is Right**
Fixed Drug Eruption is often caused by a reaction to nonsteroidal anti-inflammatory drugs (NSAIDs) such as **Diclofenac**. The exact mechanism is not fully understood, but it is thought to involve the release of histamine and other inflammatory mediators, leading to blood vessel dilation and increased permeability. The lesions typically appear within 24-48 hours of medication intake and may be accompanied by symptoms such as burning, itching, or stinging.

**Why Each Wrong Option is Incorrect**
* **Option A:** This medication is not commonly associated with FDE.
* **Option B:** This medication is more likely to cause a phototoxic reaction rather than FDE.
* **Option C:** This medication is not typically linked to FDE.

**Clinical Pearl / High-Yield Fact**
Remember the acronym **PABA** to help you remember the common causes of FDE: Phenylbutazone, Ampicillin, and **B**utazolidine (another name for Phenylbutazone).

**Correct Answer:** C. Diclofenac.