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
Herd immunity is not seen in 
Select and explain. 
A. Polio, B. Tetanus, C. Measles, D. Diphtheria
D: Diphtheria
Answer: D: Diphtheria 
Explanation: None