This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
Generation time in epidemiology is defind as - 
Select and explain. 
A. The interval between marriage and the bih of first child, B. The interval of time between primary case and secondary cases, C. The interval of time between invasion by infectious, D. agent and appearance of first sign or symptom of the disease in question
B: The interval of time between primary case and secondary cases
Answer: B: The interval of time between primary case and secondary cases 
Explanation: . generation time is defined as the time interval between the receipt of infection by a host and maximal infectivity of that host.it is roughly equal to incubation period.but not the same.generation time refers to transmission of infection whether clinical or subclinical. ref:park&;s textbook,ed 22,pg no 96