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': 'Comparison of efficacy of a new drug B with an existing drug A is done in which phase of clinical trials ? \nSelect and explain. \nA. Phase I, B. Phase II, C. Phase III, D. Phase IV', 'role': 'user'}, {'content': 'Answer: C \nExplanation: "The purpose of phase III trials is to obtain adequate data\xa0about the efficacy and safety of drugs in a larger number\xa0of patients of either sex in multiple centres usually in\xa0comparison with the standard drug."', 'role': 'assistant'}]