Patient 1 has Type A blood because agglutination occurs due to reaction with anti-B. We know that A blood group has antigen A and it is anti-B means that they attack on B type of blood cells while on the other hand, B blood group has antigen B and it is anti-A means that they will attack on the A type blood cells upon mixing. So according to the chart, there is nothing happens by reaction of the blood with anti-A whereas agglutination occur by reaction with anti-B so we can say that the patient has type A blood.
