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: Medicine
[{'content': 'The molecular basis of penicillin resistance in S.Pneumoniae is: \nSelect and explain. \nA. Alteration of penicillin-binding protein, B. Alteration in cell membranes, C. Alteration in the cell wall, D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The molecular basis of penicillin resistance in S. pneumoniae is the alteration of penicillin-binding protein (PBP) genes which result in lower affinity for penicillins. Penicillin G is the drug of choice for disease caused by susceptible organisms, including community-acquired pneumonia. Ref: Harisson, Edition - 18, Page 1156', 'role': 'assistant'}]