**Core Concept:** Diabetic nephropathy is a complication of diabetes mellitus characterized by progressive renal dysfunction and albuminuria, ultimately leading to end-stage renal disease. It is the leading cause of chronic kidney disease in developed countries.

**Why the Correct Answer is Right:** The correct answer, option D (Diabetic nephropathy), is right because the patient presents with hypertension, proteinuria, and characteristic lesions of diabetic nephropathy on renal biopsy. These symptoms and findings are specific to diabetic nephropathy, which is a complication of diabetes mellitus.

**Why Each Wrong Option is Incorrect:**

A. Essential Hypertension (hypertension without any specific cause) is less likely in a diabetic patient with proteinuria and characteristic lesions of diabetic nephropathy.

B. Nephrotic Syndrome is characterized by severe proteinuria (>3.5 g/day) and typically occurs in non-diabetic patients. It is unlikely given the diabetes and renal biopsy findings.

C. Glomerulonephritis is a group of diseases affecting the glomerulus, leading to proteinuria and hematuria. However, the renal biopsy findings in diabetic nephropathy are distinct from those in glomerulonephritis.

**Clinical Pearl:** Diabetic nephropathy is a critical complication of diabetes mellitus, mandating proper management to prevent progression to end-stage renal disease. Adequate glycemic and blood pressure control, along with regular monitoring of renal function, is essential in diabetic patients.

**Correct Answer:** Diabetic nephropathy (D) is the most likely diagnosis in this case due to the patient's diabetes mellitus, hypertension, proteinuria, and characteristic renal biopsy findings.