**Core Concept**
Basal cell carcinoma (BCC) is a type of skin cancer characterized by uncontrolled growth of basal cells in the epidermis. It is the most common subtype of skin cancer, accounting for approximately 80% of all skin cancer cases.

**Why the Correct Answer is Right**
The most common subtype of BCC is the nodular type. This is due to its tendency to present as a solitary, painless nodule on the sun-exposed areas of the skin. The nodular type of BCC arises from the basal cell layer of the epidermis and is characterized by a peripheral palisading of cells. The growth pattern of nodular BCC is often described as "pearly," with a well-defined border and a central area of necrosis.

**Why Each Wrong Option is Incorrect**
**Option A:** **Squamous cell carcinoma** is a different subtype of skin cancer, which arises from the squamous cell layer of the epidermis.
**Option B:** **Merkel cell carcinoma** is a rare type of skin cancer that arises from the Merkel cells, which are found in the basal cell layer of the epidermis, but it is not the most common subtype of BCC.
**Option C:** **Kaposi's sarcoma** is a type of skin cancer that arises from the endothelial cells, typically in immunocompromised individuals, and is not a subtype of BCC.

**Clinical Pearl / High-Yield Fact**
The "pearly" appearance of nodular BCC is a classic clinical feature that can help in its diagnosis. This appearance is due to the peripheral palisading of cells and the central area of necrosis.

**Correct Answer: C. Nodular.**