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: ENT
A 65 year old man presented with vocal cord palsy. He is a pan chewer since childhood. On examination, his abducting function of vocal cord is impaired. The nerve affected is: 
Select and explain. 
A. External laryngeal nerve, B. Recurrent laryngeal nerve, C. Mandibular nerve, D. Vagus nerve
B: Recurrent laryngeal nerve
Answer: B: Recurrent laryngeal nerve 
Explanation: The sole abductor of the vocal cords is the posterior cricoarytenoid muscle which is innervated by recurrent laryngeal nerve. Innervation of the Vocal Cord: Muscle Nerve Adductors (lateral cricoarytenoid, thyroarytenoid, interarytenoids) Recurrent laryngeal (adductor branch) Posterior cricoarytenoid Recurrent laryngeal (abductor branch) Cricothyroid External laryngeal