Answer: a) IgA
Immunoglobulin A (IgA) is an antibody that plays a crucial role in the immune function of mucous membranes.
Colostrum is a milky fluid that comes from the breasts of humans, cows, and other mammals the first few days after giving birth before true milk appears.
Immunoglobulin abundant in colostrum is IgA in the form of secretory IgA or sIgA. Much of these are produced by plasma cells in the mammary tissue.