This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: CLINICAL TRIALS, DRUG LABEL, 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 about the efficacy and safety of drugs in a larger number of patients of either sex in multiple centres usually in comparison with the standard drug." Phase I: Human Pharmacology (Non-therapeutic trials): Done in healthy persons Phase II: Therapeutic exploratory trials: conducted in patients to determine therapeutic effects, effective dose range and fuher evaluation of safety and pharmacokinetics in patients Phase III: Therapeutic confirmatory trials: Conducted to obtain adequate data about the efficacy and safety of drugs in a larger number of patients of either sex in multiple centres usually in comparison with the standard drug. Phase IV: Post marketing studies', 'role': 'assistant'}]