Question

what kind of elisa assay is shown in the diagram? a indirect b direct c sandwich

Explanation:

In direct ELISA, the primary antibody is conjugated (has the enzyme attached) and binds directly to the antigen (the yellow triangle here). The diagram shows a primary antibody conjugate binding to the antigen, with the enzyme - substrate reaction. Indirect ELISA uses a secondary antibody, and sandwich ELISA has two antibodies (capture and detection) around the antigen. So this matches direct ELISA.

Answer:

B. Direct