Which one of the following immunoglobulins constitutes the antigen binding component of B-cell receptor -a) IgAb) IgDc) IgMd) lgG

B cells display immunoglobulin molecules on their surface. These immunoglobulins serve as receptors for a specific antigen, so that each B cell can respond to only one antigen or a closely related group of antigens. All immature B cells carry Ig M immunoglobulins on their surface and most also early Ig D. Combination of cell membrane bound Ig M or Ig D with the corresponding antigen leads to specific stimulation of the B cells - either activation and cloning to produce antibody, or suppression. B cells also have surface receptors for the Fe portion of inununogloblins and for several complement components.