An African American woman noticed some bruises on her newborn girl's buttocks. She asks the nurse who spanked her daughter. The nurse explains that these marks are called:

Choice A rationale Mongolian spots are benign, flat bluish or bluish-gray birthmarks that commonly appear on the buttocks, lower back, or thighs of newborns, particularly those with darker skin tones, including African Americans, Asians, and Hispanics. They are caused by the entrapment of melanocytes (pigment-producing cells) deep within the dermis during fetal development. These spots typically fade spontaneously within a few years and are not indicative of any underlying medical condition or trauma. Choice B rationale Lanugo is fine, downy hair that covers the body of some newborns, especially preterm infants. It is usually shed within the last few weeks of gestation or shortly after birth and is unrelated to bruising or pigmented spots on the buttocks. Choice C rationale Nevus flammeus, also known as a port-wine stain, is a vascular malformation of the skin that appears as a flat, pink, red, or purple birthmark. It is caused by dilated capillaries and does not typically occur as bluish spots on the buttocks. Port-wine stains are usually permanent and may darken with age. Choice D rationale Vascular nevus, also known as a strawberry hemangioma, is a raised, red, bumpy birthmark composed of extra blood vessels. While it is a type of birthmark, it does not present as flat, bluish spots on the buttocks. Hemangiomas typically grow rapidly in the first few months of life and then gradually shrink over several years.