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
Secondary attack rate of chicken pox is around: 
Select and explain. 
A. 60%, B. 70%, C. 80%, D. 90%
D: 90%
Answer: D: 90% 
Explanation: Chicken pox is highly contagious with secondary attack rates of nearly 90%. The period of communicability ranges from 1 to 2 days before onset of rash to 4 to 5 days thereafter. Ref: Park 21st edition, page 134