Which of following technique is given in following diagram?

The method of ELISA is used for the detection of the disease using the antigen and antibody interaction. In indirect ELISA, the specific antigen is coated to the wells of the ELISA plate. The sample which contains the antibody are added to the well. If there is specific (primary) antibody, they will bind to the antigen which is coated.  The secondary antibody attached to the enzyme binds to the primary antibody. The chromogenic substrate is added which is acted upon by the enzyme and the colour is produced which can be read and detected by the ELISA reader.