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: Physiology
True about ABO blood group antigen: 
Select and explain. 
A. Found on RBC membrane, B. Glycprotein in nature, C. Highly immunogenic, D. All
D: All
Answer: D: All 
Explanation: A, B, C i.e. Found on RBC membrane; Glycprotein in nature; Highly immunogenic