Question

a protein molecule that the body identifies as foreign, triggering the immune response is a(n)
antibody.
antigen.
thrombocyte.
allergy.

Explanation:

Antigens are substances (often protein - molecules) that the body recognizes as foreign and which trigger an immune response. Antibodies are produced by the immune system in response to antigens. Thrombocytes are blood cells involved in blood - clotting, and an allergy is an over - reactive immune response to a usually harmless antigen.

Answer:

antigen