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': 'During clinical trial of drug, ethical clearance is not necessary in which phase? \nSelect and explain. \nA. Phase II, B. Phase I, C. Phase IV, D. Phase III', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Phase 4 is post-marketing surveillance where drug ethical clearance is not required. Ref: Guosheng Yin (2012) Chapter 2, Fundamentals of Clinical Trails, Clinical Trial Design: Bayesian and Frequentist Adaptive Methods, Wiley Publications, USA, Page 25 ; Goodman and Gillman, 10th Edition, Page 60', 'role': 'assistant'}]