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': 'In which of the following phases of clinical trial of drugs, ethical clearance is not required ? \nSelect and explain. \nA. Phase I, B. Phase II, C. Phase III, D. Phase IV', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]