Concept:Agglutination occurs when an antibody meets a foreign antigen that is not present in the person’s own blood.
Explanation:In blood transfusion, the recipient’s plasma contains antibodies against antigens that the recipient does not have.
If donor blood carries a contrasting antigen, the recipient’s corresponding antibody binds to it.
For example, a person with blood group A has antigen
A and anti-
B antibodies.
If blood containing antigen
B is transfused, the anti-
B antibodies react with those
B antigens.
This reaction causes red blood cells to clump together, a process called agglutination.
Therefore, agglutination is the result of a reaction between contrasting antigens and antibodies.
Answer:A. contrasting antigens and antibodies