Which of the Following Approaches to Competitive-Binding Immunoassays Would Be

Which of the following approaches to competitive-binding immunoassays would be most likely to improve the sensitivity of the assay for a specific ligand?

A) Simultaneously add the labeled and unlabeled ligand to the reaction mixture containing the appropriate antibody; measure bound labeled ligand after a fixed period of time.
B) Add the unlabeled ligand to the reaction mixture containing the appropriate antibody; allow reaction time; add the labeled ligand and allow a second reaction time; measure the bound labeled ligand
C) Add the labeled ligand to the reaction mixture containing the appropriate antibody; allow reaction time; add the unlabeled ligand and allow a second reaction time; measure the bound labeled ligand.
D) None of the above; the order of addition of the labeled ligand, the unlabeled ligand, and the antibody will have no influence on the sensitivity of the assay.