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': 'Which disease does not occur as seasonal variation- \nSelect and explain. \nA. Measles, B. Rubella, C. Gastroenteritis, D. None', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. d is None', 'role': 'assistant'}]