Which of the following statements is the most accurate characteristic of the nested case-control study?

A) A control who is selected early in the study could later develop the disease but cannot be a case in the same study.
B) In nested case-control studies, controls are a sample of individuals who are at risk for the disease at the time each case of disease develops.
C) Controls are randomly chosen from the defined cohort with which the study began.
D) The problems of possible recall bias from conventional case-control studies still remains.
E) Nested case-control studies are often less economical to conduct.

In a nested case-control study,controls are selected from noncases individuals (who are at the risk) when cases are selected."A control who is selected early in the study could later develop the disease but cannot be a case in the same study" is not correct.A control who is selected early in the study can be a case in the same study later (when the case develops the disease at that time)."Controls are randomly chosen from the defined cohort with which the study began" is not correct and is an explanation of controls in a case-cohort study Control is selected when the case is defined.."The problems of possible recall bias from conventional case-control studies still remains" is not correct.Because a nested case-control is conducted based on an earlier existing cohort study,recall bias from a conventional case-control study can be eliminated."Nested case-control studies are often less economical to conduct" is not correct.Because a nested case-control is conducted based on an earlier existing (cohort) study,it is normally considered more economical to conduct.