Final answer:
Option (c), Seborrheic keratosis is the condition that typically develops in people over the age of 30. These benign skin growths appear as waxy, scaly lesions and are often confused with skin cancer, though they are usually harmless.
Step-by-step explanation:
The condition that mainly develops in people over the age of 30 is seborrheic keratosis. Seborrheic keratosis is a benign skin growth that appears as a waxy, scaly, slightly elevated lesion, typically on the face, chest, shoulders, or back. These growths can vary in color from light tan to black, are often oval-shaped, and can range in size.
They are considered harmless and are associated with aging but can resemble skin cancer, which is why they sometimes need to be evaluated by a healthcare professional.
Unlike seborrheic keratosis, nevus (more commonly known as a mole) can appear at any age, and solar lentigines, also known as age spots or liver spots, are small, darkened areas on the skin which are also a result of sun exposure but don't have the waxy or scaly texture of seborrheic keratosis.