This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General surgery, Subject name: Surgery
[{'content': 'Absolute contraindication for endovenous abalation in varicose veins \nSelect and explain. \nA. Acute DVT, B. Varicose ulcer, C. Pregnancy, D. Chronic DVT', 'role': 'user'}, {'content': 'Answer: A \nExplanation: An acute occlusive DVT is an absolute contraindication to endovenous thermal ablation, whereas a chronically recanalized deep venous system in the extremity to be treated is a relative contraindication. Care must be taken to ensure that superficial venous ablation will not compromise the venous outflow of the post-thrombotic limb.Ref: Sabiston 20e pg: 1866', 'role': 'assistant'}]