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: Medicine
Cough of more than 3 months duration in a non-smoker with normal chest X-ray. All reasons are true EXCEPT: March 2013 (e) 
Select and explain. 
A. Post nasal drip, B. Asthma, C. Gastroesophgeal reflux, D. Common cold
D: Common cold
Answer: D: Common cold 
Explanation: Ans. D i.e. Common cold