This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Aerial disorders, Subject name: Surgery
[{'content': "Allen's test is useful on evaluating:- \nSelect and explain. \nA. Thoracic outlet compression, B. Presence of cervical rib, C. Integrity of palmar arch, D. Digital blood flow", 'role': 'user'}, {'content': "Answer: C \nExplanation: Allen's test is useful for evaluating the integrity of palmer arch.", 'role': 'assistant'}]