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
Which of these is the best study to evaluate effect and outcome? 
Select and explain. 
A. Clinical trial, B. Coho, C. Case control study, D. Cross sectional study
A: Clinical trial
Answer: A: Clinical trial 
Explanation: Ans: A. Clinical trialAmong the given options, clinical trial is the best study to evaluate effect and outcome.Randomized control trial (Experimental study or Intervention study):Considered as the ideal design to evaluate the effectiveness and the side-effects of new forms of intervention.Coho Study:A study design where one or more samples (called cohos) are followed prospectively and subsequent status evaluations with respect to a disease or outcome are conducted to determine which initial paicipants exposure characteristics (risk factors) are associated with it.