This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: JIPMER 2017, Subject name: Social & Preventive Medicine
[{'content': 'In a study, group of smokers followed up for 10 years to find incidence of a cancer. What type of study design is this? \nSelect and explain. \nA. Retrospective coho, B. Prospective coho, C. Case control study, D. Randomized control trials', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Types of coho study: 1. Prospective/Concurrent Coho Begin in present and continue to future Outcome has not yet occurred at the time the investigation begins 2. Retrospective/Historical coho Outcomes have occurred before sta of investigation Investigator goes back in time to select study groups from existing records of past employment , up to the present 3. Ambidirectional/mixed coho Combination of retrospective and prospective coho studies', 'role': 'assistant'}]