Answer:
The correct answer is - Retrospective Cohort
Step-by-step explanation:
A Retrospective cohort study is a type of observational study or research. The investigator looks back in time self-report data to see if the risk of disease was different between exposed and non-exposed patients.
The distinguishing feature, that help in identifying it, of this study is that the investigators conceive the study and begin identifying subjects after results have already been found or developed in some of the subjects.