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: Microbiology
AB blood group antigen are known as....factor ? 
Select and explain. 
A. Duffy, B. Landsteiner, C. Rhesus, D. Lutheran
B: Landsteiner
Answer: B: Landsteiner 
Explanation: Ans. is 'b' i.e., Landsteiner . Human ABO blood group system was discovered by Landsteiner.