Final answer:
A vascular nevus is a birthmark caused by an increased volume of capillaries close to the surface of the skin, presenting as a red, pink, or purple mark.
Step-by-step explanation:
An example of a birthmark caused by an increased volume of capillaries close to the surface of the skin is vascular nevus (option B). This contrasts with other skin features such as ephelides (freckles), which are areas of increased melanin production; melanocytes, which are the cells that produce melanin; and comedones, which are skin blemishes commonly associated with acne. Vascular nevus, also known as a strawberry mark, is often red, purple, or pink due to the presence of additional capillaries.