A cohort study differs from a case-control study in that:

A、Subjectsareenrolledorcategorizedonthebasisoftheirexposurestatusinacohortstudybutnotinacase-controlstudy;
B、Subjectsareaskedabouttheirexposurestatusinacohortstudybutnotinacase-controlstudy;
C、Cohortstudiesrequirefewyearstoconduct,butcase-controlstudiesdonot;
D、Cohortstudiesareconductedtoinvestigatechronicdiseases,case-controlstudiesareusedforinfectiousdiseases