This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
[{'content': 'The reaction between antibody and soluble antigen is demonstrated by \nSelect and explain. \nA. Agglutination, B. Complement fixation, C. Precipitation, D. Heamagglultination', 'role': 'user'}, {'content': 'Answer: C \nExplanation: When a soluble antigen combines with its antibody in the presence of an electrolyte (NaCl) at a suitable temperature and PH, the antigen-antibody complex forms an insoluble precipitate at a suitable temperature and pH, the antigen-antibody complex forms an insoluble precipitate.When, instead of sedimenting, the precipitate remains as floccules, the reaction is known as flocculation. Ananthanarayana 7e pg:94', 'role': 'assistant'}]