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: Dental
Which of the following is not true for incubation period? 
Select and explain. 
A. For determining isolation period of a disease, B. To prevent infection among contacts, C. For quarantine of disease, D. To differentiate among secondary cases and co-primary cases
A: For determining isolation period of a disease
Answer: A: For determining isolation period of a disease 
Explanation: None