**Core Concept**
Light microscopy in the context of nephrotic syndrome, particularly in children, is crucial for differentiating between various causes of the condition. The most common cause of nephrotic syndrome in children is minimal change disease (MCD), characterized by normal-looking glomeruli under light microscopy.

**Why the Correct Answer is Right**
In minimal change disease, the glomeruli appear normal under light microscopy due to the absence of significant glomerular lesions. The histological hallmark of MCD is the presence of foot process effacement on electron microscopy, but normal glomeruli on light microscopy. This is because the disease process primarily affects the podocytes, leading to loss of foot processes without causing significant changes visible under light microscopy. The normal appearance of the glomeruli in MCD is also associated with the good response to steroid therapy, as seen in the case described.

**Why Each Wrong Option is Incorrect**
* **Option A:** Focal segmental glomerulosclerosis (FSGS) would show segmental scarring or sclerosis in some glomeruli, which is not typical of minimal change disease.
* **Option B:** Membranous nephropathy would show thickening of the glomerular basement membrane, visible under light microscopy, which is not seen in minimal change disease.
* **Option C:** Membranoproliferative glomerulonephritis (MPGN) would show changes such as mesangial proliferation and thickening of the glomerular basement membrane, not characteristic of minimal change disease.

**Clinical Pearl / High-Yield Fact**
Minimal change disease is the most common cause of nephrotic syndrome in children and is associated with a good response to steroid therapy. Electron microscopy is essential for diagnosing MCD, showing foot process effacement, while light microscopy appears normal.

**Correct Answer:** C. Normal glomeruli.