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
The most common cause of unilateral left vocal cord palsy is - 
Select and explain. 
A. Carcinoma thyroid, B. Trauma, C. Carcinoma esophagus, D. Idiopathic
B: Trauma
Answer: B: Trauma 
Explanation: This question is tricky one.
Most common cause of left recurrent laryngeal nerve (vocal cord) paralysis is bronchial malignancy at the left hilum.
Second most common cause is iatrogenic (surgical) trauma.