This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
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? 
Select and explain. 
A. Subscapular aery, B. Superior thoracic, C. Thyrocervical trunk, D. Suprascapular aery
B: Superior thoracic
Answer: B: Superior thoracic 
Explanation: A rich anastomoses exists around the scapula between branches of subclan aery (first pa) & the axillary aery (third pa).This anastomoses provides a collateral circulation through which blood can flow to the limb when the distal pa of subclan aery or the proximal pa of axillary aery is blocked.