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': 'A coho study is - \nSelect and explain. \nA. An analytical study, B. A descriptive study, C. A corelational trail, D. An experimental study', 'role': 'user'}, {'content': "Answer: A \nExplanation: Coho study is also known as incidence study. The cohos are identified prior to the appearance of disease under investigation. The study group so defined are observed over a period of time to determine the frequency of disease among them Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 83", 'role': 'assistant'}]