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
Spontaneous pneumothorax is commonly seen in: 
Select and explain. 
A. Smokers, B. Young females, C. Old age, D. Sho statured men
A: Smokers
Answer: A: Smokers 
Explanation: Answer is A (smokers): Spontaneous pneumothorax is common in smokers. Spontaneous pneumothorax characteristically affect young, tall and thin men/boys (male gender).