Ans. is 'c' i.e., IgiMValency of antibodyo The valency of antibody refers to the number of antigenic determinants that an individual antibody molecule can bind.o The valency of all antibodies is at least two and in some instances more.AntibodyValencyIgG2IgA2,4IgM10IgD2IgE2Though the theoretical valency of Ig M is ten, this is observed only with small haptens. With larger antigens, the effective valency falls to five, probably due to steric hindrance. Physical, chemical, and Biologic Properties of Human ImmunoglobulinsPropertyIgGIgAIgMIgDIgEUsual molecular formMonomerMonomer, dimerPentamer, hexamerMonomerMonomerOther chainsNoneJ chain, SCJ chainNoneNoneSubclassesG1G2, G3, G4Al, A2NoneNoneNoneHeavy chain allotypesGm (=30)No Al, A2m (2)NoneNoneNoneMolecular mass, kDa150160, 400950, 1150175190Sedimentation constant, Sw206.6S7S, 11S19S7S8SCarbohydrate content, %3710913Serum level in average adult, mg/mL9.5-12.51.5-2.60.7-3.70.040.0003Percentage of total serum Ig75-857-155-100.30.019Serum half-life, days236532.5Synthesis rate, mg'kg per day3 365'0.40.016Antibody valency22, 430, 12O Classical complement activation+ (G1, 2?, 3)----Alternate complement activation-(G4)+-+-Binding cells via FcMacrophages neutrophils, large granular lymphocytesLymphocytesLymphocytesNoneMast cells, basophils, B cellsBiologic propertiesPlacental transfer, secondary Ab for most antipathogen responsesSecretory immunoglobulinPrimary Ab responsesMarker for mature B-cellsAllergy, antipaTasite responses