This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Naevi and vessel related disorders, Subject name: Dental
A 10 days female presents with a large patch of blue-gray pigmentation with irregular shape, unclear edges and normal skin texture involving buttocks and lower back. She is otherwise healthy and has no dysmorphic features. Which is the most probable diagnosis? 
Select and explain. 
A. Blue Nevus, B. Hematoma due to of physical abuse, C. Infantile hemangioma, D. Mongolian spot
D: Mongolian spot
Answer: D: Mongolian spot 
Explanation: Congenital dermal melanocytosis (Mongolian spot) Congenital blue-grey macule found over the sacral skin area. Pigmentation initially deepens and then regresses completely by age 7 years Blue Nevi Benign skin lesion that is four times more common in children, typically affecting the extremities and face. Small, slightly elevated, and blue-black lesions. However, blue-black papules and nodules that are new or growing must be evaluated to rule out nodular melanoma Infantile hemangioma Strawberry, capillary, or cavernous hemangioma Benign endothelial proliferation that represents the most common tumor in infancy. Most commonly on head and neck areas. Superficial ones presents as bright red-colored plaque. Deep ones presents as a soft dermal or sub cutaneous nodule with a bluish-purple color. More than 90% of untreated hemangiomas involute, that is, attain maximal regression by 9 years of age. Up to 30% of hemangiomas leave postinvolution changes including hypopigmentation, scarring, telangiectasia, and fibrofatty tissue.