Okay, let's tackle this question about post-streptococcal glomerulonephritis (PSGN). First, I need to recall the core concept. PSGN is a type of glomerulonephritis that occurs after a streptococcal infection, typically group A beta-hemolytic streptococcus. The key here is the immune complex-mediated injury.

Now, the correct answer options would likely include features like acute onset, hematuria, hypertension, and sometimes nephrotic syndrome. Also, the timing is important—PSGN usually presents 1-2 weeks after a throat infection or 3-4 weeks after a skin infection. The M-protein of the streptococcus is involved in the immune response, leading to deposition in the glomeruli.

Looking at the options, I need to figure out which statements are true. Let's think about common distractors. For example, if an option says it's caused by Staphylococcus aureus, that's wrong. Another might incorrectly state that it's a rapidly progressive glomerulonephritis (RPGN), but PSGN is usually acute but not rapidly progressive. Also, the presence of anti-streptolysin O (ASO) titers is a key diagnostic marker. If an option mentions ASO as negative, that's incorrect.

The clinical pearl here is the classic presentation: post-infectious, with signs of acute nephritis like hematuria, proteinuria, edema, and hypertension. Also, the ASO titer and complement levels (C3 is low in PSGN) are important for diagnosis.

So, the correct answer would include the association with group A streptococcus, immune complex mechanism, and the typical clinical features. The incorrect options would be other organisms, different types of glomerulonephritis, or incorrect timelines.

**Core Concept**
Post-streptococcal glomerulonephritis (PSGN) is an immune complex-mediated glomerulonephritis triggered by prior infection with **group A beta-hemolytic Streptococcus (GAS)**. It involves deposition of **anti-streptococcal antibodies** in the glomerular basement membrane, leading to inflammation and renal dysfunction.

**Why the Correct Answer is Right**
PSGN typically presents 1–2 weeks after a **pharyngeal** infection (e.g., strep throat) or 3–4 weeks after a **skin** infection (e.g., impetigo). The immune response to **M-protein** of GAS forms circulating immune complexes that deposit in the glomeruli, activating the **complement system** (C3 deficiency is common). Key features include **hematuria**, **proteinuria**, **hypertension**, and **edema**, with elevated **anti-streptolysin O (ASO) titers** confirming recent streptococcal infection.

**Why Each Wrong Option is Incorrect**
**Option A:** *Caused by Staphylococcus aureus* – PSGN exclusively follows **group A Streptococcus**, not Staphylococcus.
**Option B:** *Rapidly progressive glomerulonephritis (RPGN)* – PSGN is **acute**, not rapidly progressive. RPGN involves crescent formation

✓ Correct Answer: C. Glomerulonephritis, secondary to skin infection, is more common in summer