This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
[{'content': 'Which of the following is not a feature of a cross sectional study - \nSelect and explain. \nA. Not expensive, B. Observational study, C. Used for chronic diseases, D. Well suited for establishing interrelationships of diseases', 'role': 'user'}, {'content': "Answer: D \nExplanation: The time sequence which is essential to the concept of causativity can't be deduced from cross-sectional data. (refer pg no:69 park 23rd edition)", 'role': 'assistant'}]