This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
[{'content': 'Pressure sores usually occur when external pressure exceeds capillary occlusive pressure over \nSelect and explain. \nA. 20 mmHg, B. 25 mmHg, C. 30 mmHg, D. 35 mmHg', 'role': 'user'}, {'content': 'Answer: C \nExplanation: When external pressure exceeds the capillary occlusive pressure over 30mmHg, blood flow to skin ceases leading to tissue anoxia, necrosis and ulceration. Ref: Bailey and love 27th edition Pg no: 29', 'role': 'assistant'}]