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
Out of 10 relatives exposed to a primary case, of measles, 6 developed measles. Secondary attack rate of measles ? 
Select and explain. 
A. 10-Apr, B. 10-Jun, C. 6-Apr, D. 4-Jun
B: 10-Jun
Answer: B: 10-Jun 
Explanation: Ans. is 'b' i.e., 6/10 Secondary attack rate (SAR) SAR is defined as "the number of exposed persons developing the disease within the range of incubation period, following exposure to primary case".