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
Time period between primary case and secondary case is known as? 
Select and explain. 
A. Generation time, B. Serial interval, C. Secondary attack rate, D. Incubation period
B: Serial interval
Answer: B: Serial interval 
Explanation: Ans. is 'b' i.e., Serial interval.