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: Surgery
[{'content': 'All of the following are red flag signs of back pain except - \nSelect and explain. \nA. Previous history of malignancy, B. Previous history of steroid use, C. Saddle anaesthsia, D. Age between 35-50', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Answer- D. Age between 35-50FeaturesPrevious history malignancy (however Iong ago)Age 16< or >50 with NEW onset painWeight loss (unexplained)Previous longstanding steroid useRecent serious illnessRecent significant infectionSignsSaddle anaesthesiaReduced anal toneHip or knee weakness', 'role': 'assistant'}]