In a Study to Determine the Incidence of a Chronic

In a study to determine the incidence of a chronic disease, 150 people were examined at the end of a three-year period. Twelve cases were found, giving a cumulative risk of 8%. Fifty other members of the initial cohort could not be examined; 20 of these 50 could not be examined because they died. Which source of bias may have affected the study?

A) Information bias: interviewer/abstractor bias
B) Hawthorne effect
C) Selection bias: survival bias
D) Information bias: recall bias