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
The roots and trunks enter the posterior triangle of the neck by passing 
Select and explain. 
A. Between the anterior scalene and middle scalene muscles, B. Between the middle scalene and posterior scalene muscles, C. Behind subclavius muscle, D. Posterior and inferior subclavian Artery
A: Between the anterior scalene and middle scalene muscles
Answer: A: Between the anterior scalene and middle scalene muscles 
Explanation: The roots and trunks enter the posterior triangle of the neck by passing between the anterior scalene and middle scalene and lie posterior & superior to subclavian Artery.