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: Social & Preventive Medicine
Epidemiological marker of Hepatitis – B is 
Select and explain. 
A. HBs Ag, B. Anti - HBs, C. Anti HBc, D. HBe Ag
A: HBs Ag
Answer: A: HBs Ag 
Explanation: None