This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Screening, Subject name: Social & Preventive Medicine
All are true about "lead time" except 
Select and explain. 
A. Lead time is the period between early detection by Screening and diagnosis by other means later in life, B. Lead time is the advantage gained by screening, C. Detection programs should be restricted to those condition in which there is considerable time lag, D. None of above
D: None of above
Answer: D: None of above 
Explanation: Concept of Lead Time Lead time - Lead time is the period between early detection by Screening and diagnosis by other means later in life Lead time is the "Advantage gained by screening" Detection programs should be restricted to those conditions in which there is considerable time lag The benefits of the programme must be seen in term of its outcomes