Final answer:
Enzymes used for EIAs must possess a high degree of stability, extreme specificity, and must not be present in the antigen or antibody being tested to ensure accuracy and reliability of the assay.
Step-by-step explanation:
To be used for enzyme immunoassay (EIA), an enzyme must exhibit all of the following properties - A. A high degree of stability, B. Extreme specificity, and C. Not be present in the antigen or antibody being tested. These characteristics are essential for the precision and reliability of the test. The enzymes used in EIAs are conjugated to antibodies which specifically bind to target antigens, and upon addition of a substrate, catalyze a reaction that results in a detectable signal, often colorimetric, which signifies the presence and quantity of the antigen.