**Core Concept**
The crude birth rate (CBR) is a demographic measure that calculates the number of live births per 1,000 people in a given population. It is an essential indicator of fertility and reproductive health in a population. The CBR is calculated by dividing the number of live births in a year by the mid-year population and then multiplying by 1,000.

**Why the Correct Answer is Right**
The denominator for the crude birth rate calculation is the mid-year population of the area. This is because the mid-year population is used as a proxy for the average population size during the year. By using the mid-year population, the CBR becomes a more accurate reflection of the fertility rate in the population. The mid-year population is calculated by taking the average of the population at the beginning and end of the year.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the denominator for CBR calculation should be the mid-year population, not the total number of people in the population. Using the total population would skew the CBR calculation.
* **Option B:** This option is incorrect because the denominator for CBR calculation should be the mid-year population, not the number of women of childbearing age. While the number of women of childbearing age is relevant to fertility rates, it is not the correct denominator for the crude birth rate.
* **Option C:** This option is incorrect because the denominator for CBR calculation should be the mid-year population, not the number of live births. The number of live births is the numerator in the CBR calculation.

**Clinical Pearl / High-Yield Fact**
When calculating the crude birth rate, it's essential to use the mid-year population as the denominator to ensure an accurate reflection of fertility rates in the population.

**Correct Answer: C. Mid-year population.**