The correct option is (c) alkaline phosphatase.
Explanation:
The Enzyme Linked Immuno Sorbent Assay (ELISA), also known as the Enzyme Immuno Assay (EIA) has become a widely used serological technique for, detection of AIDS in the blood serum of HIV infected person. The enzymes used for Iabelling in ELISA include horse radish peroxidase, alkaline phosphatase; p-galactosidase, lactoperoxidase, etc.