The prefix 'mono-' in the term 'monoclonal antibody' most directly indicates which of the following?

• A. That each antibody molecule binds to only one type of antigen without any potential for cross-reactivity with related epitopes or antigens in complex biological environments, thereby ensuring absolute exclusivity of binding under all physiological conditions.
• B. That antibodies are produced from a single serum donor rather than pooled sera from multiple sources.
• C. That the antibody is monovalent (can bind only one antigen molecule), as opposed to bivalent or polyvalent forms.
• D. That the antibody population originates from a single B-cell clone producing identical antigen-binding sites.

Answer: (D)