This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Classification, Coho Study, Subject name: Social & Preventive Medicine
[{'content': 'All are disadvantages of Coho study except \nSelect and explain. \nA. Coho study involve a large number of people, B. Coho studies are expensive, C. Recall bias, D. Attrition', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Disadvantages of coho study Time consuming and Expensive Attrition - loss of follow up Hawthorne bias Ethical issues Not useful in rare disease Disadvantages of case control study Calculation of Odds ratio (Relative risk - more accurate than OR) Recall bias', 'role': 'assistant'}]