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: Pharmacology
[{'content': 'Trials stage for experimentation of adverse drug reaction in large scale population is ? \nSelect and explain. \nA. I, B. II, C. III, D. IV', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., IV o Long-term adverse effects on large number of patients -f Phase IV clinical trial.", 'role': 'assistant'}]