This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General, Subject name: Skin
[{'content': '"Going white overnight," is feature of: \nSelect and explain. \nA. Vitiligo, B. Alopecia areata, C. Anagen effluvium, D. Albinism', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. b. Alopecia areataAlopecia areata typically spares white or grey hair.Hence, if alopecia areata progresses rapidly; it will lead to this phenomenon called "going white overnight" as in a person with a mixture of grey and pigmented hair only grey hair is spared.', 'role': 'assistant'}]