**Core Concept**
Subepithelial deposits are a characteristic feature of certain types of renal diseases, particularly those involving immune complex deposition. These deposits accumulate between the glomerular basement membrane (GBM) and the overlying epithelial cells, contributing to the pathogenesis of various glomerulonephritides.

**Why the Correct Answer is Right**
In diseases like membranoproliferative glomerulonephritis (MPGN) and lupus nephritis, immune complexes composed of antibodies and antigens form and deposit in the subepithelial space. This deposition triggers an inflammatory response, leading to the proliferation of mesangial and endothelial cells, and the thickening of the GBM. The subepithelial deposits can be visualized using immunofluorescence microscopy, which helps in diagnosing these conditions.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because subepithelial deposits are not a hallmark of focal segmental glomerulosclerosis (FSGS), which is characterized by the collapse of podocyte foot processes and the accumulation of matrix material within the glomerulus.
* **Option B:** This option is incorrect because minimal change disease (MCD) is a condition characterized by the loss of foot processes of podocytes, but it does not typically feature subepithelial deposits.
* **Option C:** This option is incorrect because diabetic nephropathy involves the thickening of the GBM and the mesangial matrix, but it does not typically feature subepithelial deposits.

**Clinical Pearl / High-Yield Fact**
Subepithelial deposits can be visualized using immunofluorescence microscopy, which helps in diagnosing conditions like membranoproliferative glomerulonephritis and lupus nephritis. This technique involves labeling the deposits with specific antibodies that bind to the antigens present in the deposits.

**Correct Answer:** C. Membranoproliferative glomerulonephritis.