Which statement correctly pairs a protein category with its example?

• A. Defensive proteins include antibodies
• B. Enzymes include antibodies
• C. Hormones include antibodies
• D. Receptor proteins include antibodies

Answer: (A)

Defensive proteins protect the body from disease, and antibodies are the classic example of this group. Antibodies (immunoglobulins) are produced by immune cells and bind specifically to foreign molecules, neutralizing pathogens or marking them for attack. They are not enzymes, which catalyze chemical reactions; not hormones, which act as signaling molecules; and not receptor proteins, which receive and transmit signals at cell surfaces. So pairing defensive proteins with antibodies best captures the role and type of this protein.