**Core Concept**
Post-streptococcal glomerulonephritis (PSGN) is an immune-mediated kidney disease that occurs after a streptococcal infection, such as pharyngitis or skin infection. PSGN is characterized by the deposition of immune complexes containing streptococcal antigens and antibodies in the glomeruli, leading to inflammation and damage.

**Why the Correct Answer is Right**
The patient's history of throat infection 3 weeks ago, followed by the development of edema and hypertension, is highly suggestive of PSGN. The kidney biopsy showed normal light microscopy, which is consistent with PSGN, as the damage is often not visible under routine light microscopy. The absence of urinary symptoms and normal blood pressure further support this diagnosis.

**Why Each Wrong Option is Incorrect**
**Option A:** Nephrotic syndrome typically presents with massive proteinuria, hypoalbuminemia, and edema, which is not consistent with this patient's presentation.
**Option B:** Acute nephritic syndrome is characterized by hematuria, proteinuria, and hypertension, but the kidney biopsy showed normal light microscopy, making this diagnosis less likely.
**Option C:** Minimal change disease is a common cause of nephrotic syndrome in children, but the patient's presentation and biopsy findings do not match this diagnosis.

**Clinical Pearl / High-Yield Fact**
PSGN often presents 1-3 weeks after a streptococcal infection, and the diagnosis is often made based on the patient's history and clinical findings, rather than biopsy results.

**Correct Answer: C. Minimal change disease is a common cause of nephrotic syndrome in children, but the patient's presentation and biopsy findings do not match this diagnosis.