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': 'Which factor of S.Aureus is responsible for Coagglutination reaction? \nSelect and explain. \nA. Protein-A, B. Clumping factor, C. Hemolysin, D. Techoic acid', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Protein-A binds to Fc region of IgG leaving Fab region free to bind to an antigen, forming the basis of coagglutination reaction.', 'role': 'assistant'}]