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': 'True statement about phase 2 clinical trials is: \nSelect and explain. \nA. Large number of healthy volunteers are studied, B. Used to determine maximum tolerated dose, C. Used to determine efficacy, D. Used to determine toxicity', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]