**Core Concept**
Crude birth rate is a demographic parameter used to measure the number of live births occurring within a population per 1,000 individuals in a given time period. It is an essential indicator of fertility and reproductive health in a population.

**Why the Correct Answer is Right**
The crude birth rate is calculated by dividing the number of live births in a year by the mid-year population, multiplied by 1,000. This is the standard formula for calculating crude birth rate, which allows for comparison between different populations and time periods. The mid-year population is used as the denominator to provide an accurate representation of the population's fertility rate.

**Why Each Wrong Option is Incorrect**
**Option A:** Using the total population at the end of the year as the denominator would lead to an inaccurate representation, as it would not account for any population changes during the year.

**Option B:** Using the number of women of childbearing age as the denominator would provide a biased representation, as it would only account for a subset of the population.

**Option C:** Using the number of live births in a given time period as the numerator and the total population at the beginning of the year as the denominator would lead to an inaccurate representation, as it would not account for any population changes during the year.

**Clinical Pearl / High-Yield Fact**
When calculating demographic parameters like crude birth rate, it is essential to use the mid-year population as the denominator to ensure accuracy and comparability between different populations and time periods.

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