What is likely to occur if a person with type A blood receives type B blood?

Receiving type B blood by someone with type A blood typically leads to clumping of red blood cells, a phenomenon known as agglutination. This reaction occurs because of the presence of antibodies in the recipient's plasma. Individuals with type A blood have anti-B antibodies that will react with the B antigens present on the surface of the transfused type B red blood cells.

When type B blood is introduced into the bloodstream of a type A individual, the anti-B antibodies bind to the B antigens, leading to the cross-linking and clumping of red blood cells. This immune response can be dangerous, as it can cause hemolytic reactions and potentially severe complications, including kidney failure and shock. Therefore, the significant response when type A blood encounters type B blood is the clumping, making this the correct choice in this scenario.

In contrast, no reaction would occur in the absence of incompatible antigens and antibodies, increased blood pressure does not directly relate to the transfusion mismatch, and although allergic reactions can occur in some contexts, they are not the direct response to blood type incompatibility in this situation.