A 25-year-old male presents with gross hematuria, periorbital edema, and hypertension 2 weeks after a sore throat. Urinalysis reveals red blood cell casts and proteinuria. Serum C3 levels are decreased. Which of the following is the MOST likely diagnosis?

✓ Correct Answer: Option B

This clinical picture—acute nephritic syndrome (hematuria, edema, hypertension, RBC casts) occurring 1-3 weeks after a pharyngeal infection (sore throat) with decreased C3 levels—is classic for post-streptococcal glomerulonephritis.