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
Which of the following carriers recieved source of infection from other carriers is called - 
Select and explain. 
A. Incubatory carrier, B. Convulescent carrier, C. Healthy carrier, D. None
D: None
Answer: D: None 
Explanation: Ans. is 'None'