You are answering a USMLE-style medical question. Question: A previously healthy 17-year-old female college student comes to the emergency department because of a 1-day history of fever, chills, and severe headache. Her temperature is 39.4°C (103°F). Physical examination shows nuchal rigidity and photophobia. Blood cultures are obtained and a lumbar puncture is performed. A Gram stain of cerebrospinal fluid shows gram-negative cocci in pairs. Which of the following virulence factors was most likely involved in the initial step of this patient's infection? Options: A) Protein A B) Lipooligosaccharides C) Adhesive pili D) Biofilm formation Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.