This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
[{'content': 'Antigen-antibody binding occurs at \nSelect and explain. \nA. Center, B. Inside molecule, C. Anywhere in structure, D. Surface', 'role': 'user'}, {'content': "Answer: D \nExplanation: General features of the antigen-antibody reaction\n\nThe reaction is specific, an antigen combines with only its homologous antibody and vice versa, the specificity however is not absolute.\nAntigen-Antibody reaction requires the presence of electrolytes at a specific pH and temperature\nBonds involved in Antigen-Antibody reaction are - Van der Waal's bond, Ionic bonds, and Hydrogen bonding\nCovalent bonds are not involved \nThere is no denaturation of the antigen or antibody during the reaction\nEntire molecule of the antigen and antibody reacts\nThe combination occurs at the surface. Therefore it is surface antigens that are immunologically relevant\nThe combination is firm and reversible\nBoth antigen and antibody participate in the formation of agglutinates or precipitates.", 'role': 'assistant'}]