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
True statement about phase 2 clinical trials is: 
Select and explain. 
A. Large number of healthy volunteers are studied, B. Used to determine maximum tolerated dose, C. Used to determine efficacy, D. Used to determine toxicity
C: Used to determine efficacy
Answer: C: Used to determine efficacy 
Explanation: None