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
False about clinical trials phases of drug 
Select and explain. 
A. Healthy volunteers are taken in Phase I, B. Efficacy can be calculated in Phase II, C. Maximum drug failure occurs in phase III, D. Post marketting surveillance is done in phase IV
C: Maximum drug failure occurs in phase III
Answer: C: Maximum drug failure occurs in phase III 
Explanation: Maximum drug failure occurs in Phase II.