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
. In control of communicable diseases, the period of quarantine in respect of a disease is determined by- 
Select and explain. 
A. Incubation period, B. Infectivity period, C. Duration of illness, D. Carrier state
A: Incubation period
Answer: A: Incubation period 
Explanation: None