This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Upper Limb and Lower Limb, Subject name: Anatomy
What are root values of nerve supplying muscle needed for latter pa of the following action? 
Select and explain. 
A. C7, C8, B. C8, T1, C. C5, C6, D. C5, C6, C7
D: C5, C6, C7
Answer: D: C5, C6, C7 
Explanation: Serratus Anterior is responsible for the latter pa of abduction along with trapezius. The long thoracic nerve (Nerve of Bell) originates from the C5-C7 roots and descends in the axilla, posterior to the brachial plexus, to innervate the serratus anterior muscle.