Question

explain why blood from a donor of group A cannot be transfused to a blood recipient of group B

Answer 1

If an individual with blood group B receives blood from a donor having A  blood group, it leads to immunological reaction which causes agglutination(clumping) of RBC in the body of the​ recepient. Individual with B blood group has anti-A antibody in blood which produce immunological reaction with A antigen present in the RBC of the donor.