This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
A disease whose etiology is not known, the first step in the formation of hypothesis will be- 
Select and explain. 
A. Cross sectional study, B. Descriptive Epidemiology, C. Case control study, D. Coho study
B: Descriptive Epidemiology
Answer: B: Descriptive Epidemiology 
Explanation: in descriptive epidemilogy,it is regarded as the first phase of epidemiological investigations.the basic procedures in a descriptive study includes, 1.defining the poppulation at risk. 2.defining the disease under study. 3.describing the disease by time,place and person. 4.measurement of the disease. 5.comparing with known indices. 6.formulation of an aetiological hypothesis. ref:park&;s textbook,ed 22,pg no 60