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: Social & Preventive Medicine
Case control study, All can be measured except - a) Relative risk b) Incidence c)  Odds ratiod)  Cause & effect relation 
Select and explain. 
A. cb, B. b, C. abd, D. da
C: abd
Answer: C: abd 
Explanation: None