This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
[{'content': 'There is defect in production of melanin in all except \nSelect and explain. \nA. Albinism, B. Melasma, C. Vitiligo, D. Piebaldism', 'role': 'user'}, {'content': 'Answer: B \nExplanation: In melasma etiology is ultra violet rays. It is also triggered by pregnancy and oral contraceptive pills.\nAll the other given conditions are associated with defects in melanin production.', 'role': 'assistant'}]