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': 'In a Subclan aery block at the outer border of 1st rib, all of the following aeries help in maintaining the circulation to upper limb except \nSelect and explain. \nA. Subscapular aery, B. Superior thoracic, C. Thyrocervical trunk, D. Suprascapular aery', 'role': 'user'}, {'content': "Answer: B \nExplanation: In distal subclan & proximal axillary aery block aerial anastomosis exists between 1st pa of SCA&3RD pa OF axillary aery Ref: Gray's 40e/p447-451", 'role': 'assistant'}]