**Core Concept**
Post-infective glomerulonephritis, also known as post-streptococcal glomerulonephritis (PSGN), is an immune complex-mediated glomerulonephritis triggered by a preceding streptococcal infection. This condition 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 correct answer is related to the clinical presentation of PSGN. The condition typically presents with hematuria (blood in the urine), proteinuria (excess protein in the urine), and oliguria (reduced urine output). Renal failure may also occur in severe cases. The hematuria is often accompanied by red blood cell casts, which are cylindrical collections of red blood cells that form in the renal tubules and are indicative of glomerular damage.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because PSGN typically does not present with nephrotic syndrome, which is characterized by massive proteinuria, hypoalbuminemia, and edema. While some patients with PSGN may have mild proteinuria, nephrotic syndrome is not a typical feature of this condition.
**Option B:** This option is incorrect because PSGN is not typically associated with the nephritic syndrome of systemic lupus erythematosus (SLE). While both conditions can present with hematuria and renal failure, PSGN is a distinct entity that is triggered by a streptococcal infection, whereas SLE is a systemic autoimmune disease.
**Option C:** This option is incorrect because PSGN is not typically associated with the renal manifestations of diabetes mellitus. While diabetes can cause renal damage and lead to chronic kidney disease, PSGN is a separate condition that is triggered by a streptococcal infection.

**Clinical Pearl / High-Yield Fact**
A key feature of PSGN is the presence of red blood cell casts in the urine, which are indicative of glomerular damage. This is a classic exam question trap: remember that PSGN is an immune complex-mediated glomerulonephritis that presents with hematuria, proteinuria, and oliguria, and is often accompanied by red blood cell casts.

**Correct Answer: C. Nephritic syndrome**