**Core Concept**
The question is testing the association between exposure to environmental toxins, specifically heavy metals, and the development of skin cancers, specifically basal cell and squamous cell carcinomas. The key concept here is the role of arsenic (As) as a known human carcinogen, particularly in the development of skin cancers.

**Why the Correct Answer is Right**
Arsenic (As) is a heavy metal that has been widely used in the form of chromated copper arsenate (CCA) in pressure-treated lumber, as well as in insecticides and herbicides. Prolonged exposure to arsenic has been linked to an increased risk of skin cancers, particularly basal cell and squamous cell carcinomas. Arsenic can accumulate in the body and cause chronic toxicity, leading to the development of skin lesions, including those on the palms and soles. The greenish hue of the pressure-treated lumber is a giveaway for the presence of arsenic.

**Why Each Wrong Option is Incorrect**
**Option A:** Cadmium (Cd) is another heavy metal that can cause toxicity, but it is more commonly associated with kidney damage and prostate cancer.
**Option B:** Lead (Pb) is a well-known neurotoxin and can cause developmental delays in children, but it is not as strongly linked to skin cancers as arsenic.
**Option C:** Mercury (Hg) is a heavy metal that can cause neurological toxicity and kidney damage, but it is not as commonly associated with skin cancers as arsenic.

**Clinical Pearl / High-Yield Fact**
This is an example of a classic case of "environmental disease," where exposure to environmental toxins can lead to chronic disease. Remember that arsenic exposure is not limited to drinking water; it can also occur through skin contact with contaminated soil or through inhalation of arsenic-rich particles.

**Correct Answer:** C. Arsenic (As)