A person suspected to suffer from AIDS is advised to undergo ............ diagnostic test.

The correct option is D ELISA

• ELISA (Enzyme-linked immunosorbent assay) is used as a diagnostic test for identification of HIV virus. The assay uses a solid-phase enzyme immunoassay (EIA) to detect the presence of a ligand (commonly a protein) in a liquid sample using antibodies directed against the protein to be measured.
• In ELISA, antigens from the sample are attached to a surface. Then, a matching antibody is applied over the surface so it can bind to the antigen. This antibody is linked to an enzyme, and in the final step, a substance containing the enzyme's substrate is added. The subsequent reaction produces a detectable signal, most commonly a colour change in the substrate.
  
• So, the correct answer is 'ELISA'.