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
The only disease which has been eradicated ? 
Select and explain. 
A. Chickenpox, B. Smallpox, C. Measles, D. Measles
B: Smallpox
Answer: B: Smallpox 
Explanation: Ans. is 'b' i.e., Smallpox "Today, smallpox is the only disease that has been eradicated".