**Core Concept**
The question is testing the ability to identify a specific histological diagnosis in a patient with nephrotic syndrome who is unresponsive to steroids. This patient's history of IV drug abuse and failure to respond to steroids points towards a specific type of glomerular disease.

**Why the Correct Answer is Right**
The patient's presentation is consistent with membranoproliferative glomerulonephritis (MPGN), a type of glomerular disease characterized by the deposition of immune complexes and complement proteins in the glomeruli. MPGN is often associated with chronic infections or autoimmune diseases, and in this case, the patient's history of IV drug abuse suggests a possible link to hepatitis C virus (HCV) infection, which is a known risk factor for MPGN. The failure to respond to steroids is also consistent with MPGN, as it is often resistant to immunosuppressive therapy.

**Why Each Wrong Option is Incorrect**
* **Option A:** Focal segmental glomerulosclerosis (FSGS) is a common cause of nephrotic syndrome, but it is typically responsive to steroids, making it an unlikely diagnosis in this case.
* **Option B:** Minimal change disease (MCD) is another common cause of nephrotic syndrome, but it is also typically responsive to steroids and does not have a strong association with IV drug abuse or HCV infection.
* **Option D:** Diabetic glomerulosclerosis is a cause of nephrotic syndrome in patients with diabetes, but it does not have a strong association with IV drug abuse or HCV infection, and is not typically characterized by aggressive disease.

**Clinical Pearl / High-Yield Fact**
In patients with nephrotic syndrome who are unresponsive to steroids, a renal biopsy should be performed to rule out MPGN, which is a potentially life-threatening condition that requires specific treatment.

**Correct Answer:** C. Membranoproliferative glomerulonephritis (MPGN)