This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Infection, Subject name: Medicine
[{'content': 'A 5-year-old boy presents with ear pain and fever. The left eardrum is inflamed with a small perforation in it and pus is seen in the external canal. A swab of the area grows S. pneumoniae. Which of the following is the most likely mechanism for S. pneumoniae to cause otitis media? \nSelect and explain. \nA. hematogenous spread, B. direct extension from the nasopharynx, C. direct inoculation on the ear, D. spread through lymphatic tissue', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Infections of the middle ear, trachea, sinuses, bronchi, and lungs are caused by direct spread from nasopharyngeal colonization. Disease of the CNS, heart valves, bones, joints, and peritoneal are usually caused by hematogenous dissemination.', 'role': 'assistant'}]