This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oesophagus, Subject name: Surgery
[{'content': 'Which amongst following is the most common cause of UTI \nSelect and explain. \nA. Instrumentation, B. Urethral diverticulum, C. Bladder stones, D. Pregnancy', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) InstrumentationRef: Harrison 18th ed. / 288* Urethral catheterization is the single most important predisposing factor in the development of nosocomial urinary tract infection. Cystoscopy may be followed by a transient bacteremia.* The most important risk factor for bacteriuria is the presence of a catheter. Eighty percent of nosocomial UTIs are related to urethral catheterization, while 5-10% are related to genitourinary manipulation. Catheters inoculate organisms into the bladder and promote colonization by providing a surface for bacterial adhesion and causing mucosal irritation.', 'role': 'assistant'}]