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: Gynaecology & Obstetrics
[{'content': 'Cystitis is most commonly caused by : \nSelect and explain. \nA. E. coli, B. Pseudomonas, C. Proteus mirabilis, D. Neisseria gonorrhea', 'role': 'user'}, {'content': 'Answer: A \nExplanation: E. coli', 'role': 'assistant'}]