This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Demography and family planning, Subject name: Social & Preventive Medicine
In calculating crude bih rate which of the following is used as denominator 
Select and explain. 
A. Women in 15-49 yrs age group, B. All persons in 15-49 yrs age group, C. Mid year population, D. All live bihs
C: Mid year population
Answer: C: Mid year population 
Explanation: Bih rate = Number of live bihs during the year X 1000 / Estimated mid year population Unsatisfactory measure of feility because the total population is not exposed to child bearing Reference : Park&;s textbook of preventive and social medicine, 23rd edition, pg no: 488