This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General Pharmacology, Subject name: Pharmacology
[{'content': 'Which phase of clinical trials is done after the drug enters the market? \nSelect and explain. \nA. Phase I, B. Phase II, C. Phase III, D. Phase IV', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. (D) Phase IV(Ref: KDT 8th/e 91)Clinical TrialOther NamePhase 0Microdosing studiesPhase IHuman pharmacology and safetyPhase IITherapeutic exploratoryPhase IIITherapeutic confirmatoryPhase IVPost marketing surveillance', 'role': 'assistant'}]