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: Surgery
Which of the following is main etiological factor for Hidradenitis suppurativa 
Select and explain. 
A. Smoking, B. Diabetes, C. Steroid use, D. Obesity
A: Smoking
Answer: A: Smoking 
Explanation: Smoking is the main etiological factor for Hidradenitis suppurativa.