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: Social & Preventive Medicine
[{'content': 'Researchers surveyed the causes of vitamin D deficiency and its geographic distribution. They found that exposure to ultra violet rays is crucial for its adequacy, which when get excessively filtered by the skin result in its deficiency. This deficiency is more common in \nSelect and explain. \nA. Asians, B. Black Africans, C. Mongoloids, D. Europeans', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]