A Recent Study Found That Screening for Disease X Led

A recent study found that screening for disease X led to increased survival.In the study,those who were screened were generally younger,healthier,and more aware of their health than those who were not screened.This makes it hard to evaluate whether the improvement in survivorship was due to the screening program or due to the characteristics of those who are screened.What is the name of this issue when evaluating the effect of a screening program?

A) Lead time bias
B) Overdiagnosis bias
C) Selection bias
D) Misclassification bias
E) Length-biased sampling