This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nerve supply, Nerve Lesions, Subject name: Anatomy
All are true about brachial plexus EXCEPT:- 
Select and explain. 
A. Lower trunk is formed by root C8 and T1, B. Lateral cord is formed by upper and middle trunk, C. Posterior cord is formed by posterior divisions of all three trunks, D. C4 root is post fixed to plexus
D: C4 root is post fixed to plexus
Answer: D: C4 root is post fixed to plexus 
Explanation: Contribution by C4 to brachial plexus is pre-fixed brachial plexus. Post-fixed brachial plexus has contribution by T2 Brachial plexus is formed by the anterior primary rami of C5, 6, 7, 8 & T1 It consists of roots, trunks, cords, divisions and branches. A total of 17 branches are given off from the plexus including 2 from roots, 2 from trunks and 13 from cords.