Concept:Mixing incompatible blood groups triggers an antigen-antibody reaction that causes red blood cells to clump.
Explanation:Blood containing antigen A is mixed with blood that contains antibody a, also known as anti-A.
The antibody a specifically recognises and binds to antigen A on the surface of red blood cells.
Since each antibody can attach to more than one red blood cell, it forms bridges between the cells.
This cross-linking makes the red blood cells clump together.
This clumping process is called agglutination.
The reaction does not dissolve clots, change the blood group, or leave the blood composition unaffected.
Answer:A. lead to agglutination