This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, Subject name: Microbiology
[{'content': 'Virulence of gonococci is due to \nSelect and explain. \nA. Pili, B. Endotoxin, C. Exotoxin, D. None', 'role': 'user'}, {'content': "Answer: A \nExplanation: Pili: hair like structures several micrometers long. Acts as a virulence factor by promoting attachment to host cells and inhibiting phagocytosis. Pili are composed of repeating peptide subunits consisting of conserved and variable regions. Pili undergo antigenic and phase variations. Reference: Textbook of Microbiology; Anathanarayan and panicker's; 10th edition; Page no: 234", 'role': 'assistant'}]