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
Phase 4 clinical trial also called as? 
Select and explain. 
A. Human pharmacology and safety, B. Post marketing surveillance, C. Therapeutic exploration and dose ranging, D. Therapeutic confirmation
B: Post marketing surveillance
Answer: B: Post marketing surveillance 
Explanation: None