In the Context of Case Studies,which of the Following Is

In the context of case studies,which of the following is true?

A) In case studies,a researcher studies a single individual or very small group in depth.
B) Case studies are not based on retrospective self-report and so are most accurate.
C) In case studies,researchers observe the present condition of the subject and not their previous history.
D) The generalizability of case studies is the highest among all the research methods related to sex research.
E) In case studies,researchers typically use indirect observation methods in which the participants are not aware that they are being studied.