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
Maximum tolerated dose of a new drug is evaluated in: 
Select and explain. 
A. Phase 1, B. Phase 2, C. Phase 3, D. Phase 4
A: Phase 1
Answer: A: Phase 1 
Explanation: Phase 1 clinical trial: Used to evaluate Maximum tolerated dose (MTD) of a new drug. Healthy human volunteers are used. Done for safety and non-toxicity.