The correct option is D IgA
Immunoglobulins are antibodies. They are proteins that are made by our immune system after exposure to an antigen (something alien or foreign to our body that causes an immune response). Immunoglobulins or antibodies, fight off germs, illness and disease.
Secretory immunoglobulin A(SIgA) is a special immunoglobulin. It is the main antibody found in breast milk. Besides IgA, breast milk also contains other antibodies like IgE, IgG, IgM and IgD.
IgG is the most abundant antibody in the blood.