This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Trauma, Subject name: Surgery
[{'content': 'Allen&;s test is useful in evaluating \nSelect and explain. \nA. Thoracis 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: it is done to find out the patency of radial and ulnar aeries. both the aeries are compressed near the wrist and allowed to blanch completely in one minute(in the mean time patient closes and opens the fist several times for fuher venous outflow). palm appears pale and white. one of the aeries is released and colour of hand is noted. normally hand will become pink and flushed in no time; whereas in obstruction, the area will still remain pale. other aery is also released and looked for changes in hand. (Ref: SRB&;s Manual of Surgery, 5th edition, pg no. 173)', 'role': 'assistant'}]