**Core Concept**
Nephrotoxicity refers to the adverse effects of certain substances on the kidneys, leading to impaired renal function or damage to the renal parenchyma. This can be caused by various factors, including medications, toxins, and diseases.

**Why the Correct Answer is Right**
The correct answer is **A. Amphotericin B**. Amphotericin B is an antifungal medication that is known to cause nephrotoxicity as a side effect. This is due to its ability to bind to the cell membranes of renal cells, leading to increased permeability and ultimately, cell death. The resulting renal damage can manifest as acute kidney injury, characterized by decreased urine output, increased serum creatinine levels, and electrolyte imbalances.

**Why Each Wrong Option is Incorrect**
**Option B:** Vancomycin is an antibiotic that can cause nephrotoxicity, but it is less likely to cause severe renal damage compared to Amphotericin B. While Vancomycin can cause acute kidney injury, it is often reversible with discontinuation of the medication.

**Option C:** Cephalosporins are a class of antibiotics that are generally well-tolerated and do not commonly cause nephrotoxicity. However, some cephalosporins may cause interstitial nephritis, which is a different type of renal injury.

**Option D:** Furosemide is a loop diuretic that is commonly used to treat hypertension and edema. While Furosemide can cause electrolyte imbalances and dehydration, it is not typically associated with nephrotoxicity.

**Clinical Pearl / High-Yield Fact**
It's essential to note that nephrotoxicity can be prevented or minimized by monitoring serum creatinine levels and urine output, adjusting the dosage of nephrotoxic medications, and using alternative medications when possible.

**Correct Answer:** A. Amphotericin B.