This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Communicable diseases, Subject name: Social & Preventive Medicine
A herd immunity of over -% is considered necessary to prevent epidemic spread of diphtheria- 
Select and explain. 
A. 50%, B. 55%, C. 60%, D. 70%
D: 70%
Answer: D: 70% 
Explanation: <p> A herd immunity of over 70% is considered necessary to prevent epidemic spread of diphtheria. Park&;s textbook of preventive and social medicine,K.Park,22nd edition,page no:151 <\p>