Ans. is 'b' i.e., IgG Immunoelectrophoresis in multiple myeloma* Electrophoretic analysis permits separation of components of the serum proteins.* The immunoglobulins move heterogeneously in an electric field and form a broad peak in the gamma region. The g globulin region of the electrophoretic pattern is usually increased in the sera of patients with plasma cell tumors. There is a sharp spike in this region called an M component (M for monoclonal).* The monoclonal antibody must be present at a concentration of at least 5 g/L (0.5 g/dL) to be accurately quantitated by this method. This corresponds to -109 cells producing the antibody.* Confirmation that such an M component is truly monoclonal and the type of immunoglobulin is determined by immunoelectrophoresis that reveals a single heavy and/or light chain type.* Hence immunoelectrophoresis and electrophoresis provide qualitative and quantitative assessment of the M component, respectively.* The serum M component in multiple myeloma will be IgG in 53% of patients, IgA in 25%, and IgD in 1%; 20% of patients will have only light chains in serum and urine.