Explain why blood group A cannot be transfused to blood group B

That implies individuals with type A blood make antibodies against B antigens. An individual with type A blood getting a transfusion of type B or AB blood would have an ABO inconsistency response. In an ABO contradiction response, your resistant framework assaults the fresh blood cells and devastates them.

People with type A blood create antibodies against B antigens. There would be a incompatibility reaction if A blood type was mixed with B blood type. In an ABO incompatibility the reaction would be your immune system attacking the new blood cells and destroying them