This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
Case control study : 
Select and explain. 
A. Is a prospective study, B. Gives Odd ratio, C. Useful in case of rare disease, D. Both 2 and 3
D: Both 2 and 3
Answer: D: Both 2 and 3 
Explanation: Case control:

A retrospective study.
Risk factor is to be identified — disease present 
Gives Odds ratio.
Best method to study RARE disease — Case control study.

NESTED Case-control study

It is a case-control study nested within COHORT study. So, it is a prospective study.