This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: RCT, Trials, Subject name: Social & Preventive Medicine
[{'content': 'Healthy human volunteers are the Unit of study in ___ Phase of Clinical trial:- \nSelect and explain. \nA. Phase I, B. Phase II, C. Phase III, D. Phase IV', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Phase Unit of study Purpose Phase 0 Healthy human volunteers Micro-dosing Phase 1 Healthy human volunteers Safety and non-toxicity profile Phase II Patients Effectiveness Phase III Patients Comparison with existing drugs Phase IV Patients Long term side effects / post marketing', 'role': 'assistant'}]