Concept:Blood group O contains anti-A and anti-B antibodies, so it can accept only blood lacking A and B antigens.Explanation:A person with blood group O has antibodies against both antigen A and antigen B.If donated blood contains either antigen A or antigen B, it will cause a dangerous immune reaction.Only group O red blood cells have neither A nor B antigens.Therefore, a person with blood group O can receive blood only from group O donors.Answer:A. group O only