**Core Concept**
Arsenic poisoning leads to the accumulation of arsenic and its metabolites in the body, primarily affecting the liver, kidneys, and skin. The chronic exposure to arsenic results in its deposition in the connective tissue and bone, causing various systemic effects.

**Why the Correct Answer is Right**
The most common finding in chronic arsenic poisoning is the presence of Mees' lines, which are white or grayish lines that appear on the nails due to the deposition of arsenic in the nail matrix. This occurs as a result of the arsenic binding to the keratin in the nail plate, causing its fragmentation and discolouration. Mees' lines are a classic sign of chronic arsenic poisoning and can be seen in individuals exposed to high levels of arsenic for an extended period.

**Why Each Wrong Option is Incorrect**
**Option A:** While arsenic can cause gastrointestinal symptoms, such as nausea and vomiting, in acute poisoning, it is not the most characteristic finding in chronic arsenic poisoning.
**Option B:** Arsenic can cause skin lesions and hyperpigmentation, but these are not as specific as Mees' lines for chronic arsenic poisoning.
**Option C:** Arsenic exposure can lead to increased risk of certain cancers, but this is not a direct finding in the body.
**Option D:** This option is incomplete.

**Clinical Pearl / High-Yield Fact**
Mees' lines are a classic sign of chronic arsenic poisoning and can be seen in individuals exposed to high levels of arsenic for an extended period. This sign is often accompanied by other systemic effects, such as skin lesions and gastrointestinal symptoms.

**Correct Answer: B. Arsenic can cause skin lesions and hyperpigmentation, but these are not as specific as Mees' lines for chronic arsenic poisoning.**