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': 'Criteria for “Problem village” include all except \nSelect and explain. \nA. Risk of Guinea worm infection, B. Water is more than depth of 15 meter, C. There is excess of Na+, K+, F+ salts, D. Where no water source in a distance of 1.6 km from community', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]