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
While investigating an epidemic, search for more cases is continued till what period ? 
Select and explain. 
A. Twice the incubation period of the disease since occurrence of the last case, B. Thrice the incubation period of the disease since occurrence of the case, C. The longest incubation period for the disease, D. Incubation period for the disease plus two standard deviations
A: Twice the incubation period of the disease since occurrence of the last case
Answer: A: Twice the incubation period of the disease since occurrence of the last case 
Explanation: None