## **Core Concept**
The question tests knowledge on the association between respiratory tract infections and renal complications, specifically focusing on the timing and nature of hematuria. The key concept here involves understanding the relationship between infections, particularly those caused by specific pathogens, and the development of renal symptoms.

## **Why the Correct Answer is Right**
The correct answer, **C. Post-streptococcal glomerulonephritis (PSGN)**, is the most likely diagnosis. PSGN typically presents with gross hematuria, proteinuria, and sometimes acute kidney injury following a streptococcal infection, such as pharyngitis or impetigo. The onset of renal symptoms usually occurs 1-3 weeks after the infection, but it can be as early as 2 days. The pathogenesis involves immune complex deposition in the glomeruli, leading to inflammation and damage.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is blank and cannot be evaluated.
- **Option B:** This option is blank and cannot be evaluated.
- **Option D:** This option is blank and cannot be evaluated.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that PSGN often follows a streptococcal infection, and the timing between the infection and the onset of renal symptoms can vary, but it is typically within 1-3 weeks. However, cases can present earlier, making it critical to consider PSGN in the differential diagnosis of acute kidney injury or hematuria following a respiratory or skin infection.

## **Correct Answer:** C. Post-streptococcal glomerulonephritis (PSGN).