**Core Concept**
Arsenic poisoning is a medical condition caused by the ingestion, inhalation, or absorption of arsenic, a toxic element. The distribution of arsenic in the body is crucial for understanding its toxic effects. Arsenic tends to accumulate in tissues with high sulfur content.

**Why the Correct Answer is Right**
The correct answer is related to the fact that arsenic binds to sulfur-containing compounds, such as keratin, which is abundant in hair and nails. As a result, the greatest amount of arsenic is often found in these tissues. The mechanism involves the substitution of arsenic for phosphorus in various biochemical reactions, leading to the disruption of cellular processes.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while arsenic can be found in the liver, it is not the primary site of accumulation.
**Option B:** This option is incorrect because the kidneys do play a role in excreting arsenic, but they do not retain the highest amount.
**Option C:** This option is incorrect because the lungs are a common site of entry for inhaled arsenic, but they do not typically accumulate the greatest amount.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that arsenic poisoning can be diagnosed by analyzing hair or nail samples, as these tissues tend to retain high levels of the toxin. This method can be particularly useful in cases where exposure occurred months or even years prior to diagnosis.

**Correct Answer:** D. Hair and Nails