**Core Concept**
Mercury is a heavy metal that can cause nephrotoxicity, leading to renal damage. The kidney's structure and function are particularly vulnerable to mercury's toxic effects.

**Why the Correct Answer is Right**
Mercury accumulates in the proximal convoluted tubules (PCT) of the nephron, causing damage to the tubular cells and leading to acute tubular necrosis. The PCT is responsible for reabsorbing glucose, amino acids, and other essential nutrients from the filtrate, and mercury's presence disrupts this process. The PCT's high metabolic rate and rich blood supply make it more susceptible to mercury's toxic effects.

**Why Each Wrong Option is Incorrect**
**Option A:** The glomerulus is the part of the nephron where filtration occurs, but it is not the primary site of mercury toxicity.
**Option B:** The distal convoluted tubule (DCT) is involved in electrolyte and acid-base balance, but it is not the primary site of mercury accumulation.
**Option C:** The collecting duct is responsible for water reabsorption and electrolyte regulation, but it is not directly affected by mercury toxicity.

**Clinical Pearl / High-Yield Fact**
Mercury poisoning can be prevented by minimizing exposure to mercury-containing compounds, using personal protective equipment, and following proper laboratory protocols.

**Correct Answer: A. The proximal convoluted tubules (PCT) of the kidney are affected by Mercury.**