**Core Concept**
Diabetic nephropathy is a common complication of diabetes mellitus characterized by thickening of the glomerular basement membrane, mesangial expansion, and diffuse loss of foot processes in podocytes on electron microscopy.

**Why the Correct Answer is Right**
The diffuse loss of foot processes in podocytes is a hallmark feature of diabetic nephropathy. This loss is associated with the accumulation of electron-dense deposits in the region of hyalinosis and sclerosis within the glomerulus. These deposits are composed of amyloid-like fibrils and are thought to contribute to the progression of diabetic nephropathy. The diffuse loss of foot processes impairs the normal function of the glomerular filtration barrier, leading to proteinuria and eventual renal failure.

**Why Each Wrong Option is Incorrect**
* **Option A:** This is incorrect because while membranous nephropathy does feature subepithelial electron-dense deposits, it is not typically associated with diffuse loss of foot processes or hyalinosis/sclerosis.
* **Option B:** This is incorrect because minimal change disease is characterized by normal electron microscopy, with the exception of occasional podocyte effacement.
* **Option C:** This is incorrect because focal segmental glomerulosclerosis (FSGS) is a cause of nephrotic syndrome, but it typically presents with segmental rather than diffuse loss of foot processes.

**Clinical Pearl / High-Yield Fact**
The diffuse loss of foot processes in diabetic nephropathy is a critical feature that distinguishes it from other causes of nephrotic syndrome, such as minimal change disease and FSGS.

**Correct Answer: D. Diabetic nephropathy**