The diagram shows the simplified structure of a lateral flow immunochromatographic assay (diagnostic test strip) used in healthcare for monitoring and maintaining health (such as a rapid antigen test or pregnancy test).
Which of the following correctly describes the role of the immobilised antibodies located at the Control Line (CCC)?
They bind specifically to the target antigen (such as viral proteins or hCG) to show a positive test result.
They bind directly to the mobile antibody-dye conjugates that have migrated from the conjugate pad, confirming that the test is valid and the fluid has successfully run.
They act as non-specific blocking proteins to prevent any excess target antigen from reaching the absorption pad.
They release mobile dye-carrying latex beads into the flow path to initiate the capillary movement of the fluid.