Final answer:
The nevus on Vern's nail was probably caused by genetics.
Step-by-step explanation:
The nevus on Vern's nail was probably caused by genetics. Some skin conditions and abnormalities, including nevi, can be inherited. Nevi are typically harmless and caused by an overgrowth of melanocytes, which are pigment-producing cells. They can appear on the skin or nails and vary in color, size, and shape.