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: Social & Preventive Medicine
In a study to establish smoking as a risk factor for disease, 30 out of 50 smokers developed disease while as 10 out of 50 non smokers developed disease. The Odds ratio is: 
Select and explain. 
A. 3, B. 5, C. 6, D. 10
B: 5
Answer: B: 5 
Explanation: 5