The clumping together of red blood cells by the action of an antibody is known as: serology clotting radioimmunology agglutination blood typing

## Step 1<br />The problem is asking for the term that describes the clumping together of red blood cells by the action of an antibody. This is a process that occurs when an antigen (a substance that triggers an immune response) is present in the blood. The antibodies bind to the antigens, causing the red blood cells to clump together.<br /><br />## Step 2<br />Let's analyze each of the given options:<br /><br />- Serology: This is a branch of medical science that deals with the detection and identification of antibodies in the blood. It does not describe the clumping of red blood cells.<br /><br />- Clotting: This refers to the process of blood coagulation, which is the formation of a clot to stop bleeding. It does not describe the clumping of red blood cells.<br /><br />- Radioimmunology: This is a branch of immunology that uses radioisotopes to study the immune system. It does not describe the clumping of red blood cells.<br /><br />- Agglutination: This is the process where cells or particles adhere to each other to form clumps. In the context of blood, it refers to the clumping of red blood cells due to the action of antibodies.<br /><br />- Blood typing: This refers to the classification of blood based on the presence or absence of certain antigens on the surface of red blood cells. It does not describe the clumping of red blood cells.<br /><br />## Step 3<br />Based on the above analysis, the term that best describes the clumping together of red blood cells by the action of an antibody is 'agglutination'.