**Core Concept**
The underlying principle being tested is the pathophysiology of reversible lens granular deposits, which is related to **lens metabolism** and **osmotic balance**. This condition is often associated with **diabetes mellitus** and other metabolic disorders.

**Why the Correct Answer is Right**
Reversible lens granular deposits, also known as **sorbitol** accumulation, occur due to the **aldose reductase** pathway. In this pathway, glucose is converted to sorbitol, which accumulates in the lens and causes **osmotic swelling**.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it is not directly related to the **aldose reductase** pathway.
**Option B:** Incorrect as it is not associated with **lens metabolism**.
**Option C:** Incorrect because it does not involve **sorbitol** accumulation.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that **reversible lens granular deposits** are often seen in **uncontrolled diabetes**, highlighting the importance of **tight glycemic control**.

**Correct Answer:** D. Sorbitol