<prompt> Complement attaches to immunoglobulin at:AminoterminalFab regionVariable regionFc fragment  <response>: Ans. is d i.e., Fc fragment Ref: Ananthanarayan, 8the, p. 97 Fc fragment consist of parts of both H chains, composed of carboxyterminal portion of the H chains and it determines biological properties of Ig molecule such as complement fixation, placental transfer, skin fixation and catabolic rate. 