## Core Concept
The question tests knowledge of toxicology, specifically the treatment of heavy metal poisoning. Arsenic poisoning is a significant concern due to its high toxicity and potential for exposure. The treatment involves using specific antidotes that can chelate or neutralize the toxin.

## Why the Correct Answer is Right
The correct answer, **D. Succimer (or DMSA)**, is a chelating agent used in the treatment of heavy metal poisoning, including lead, mercury, and arsenic. Succimer works by binding to the metal ions, forming a stable complex that can be excreted from the body, thereby reducing the toxic effects of the metal.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is blank and does not provide a valid choice for consideration.
- **Option B:** This option is also blank and does not offer a viable antidote for arsenic poisoning.
- **Option C:** Similarly, this option is blank and lacks a specific antidote.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **penicillamine** and **dimercaprol** are also used as chelating agents in heavy metal poisoning, but **succimer (DMSA)** is particularly noted for its oral bioavailability and safety profile, making it a preferred option for outpatient treatment of arsenic poisoning.

## Correct Answer: D. Succimer.