**Core Concept**
The General Fertility Rate (GFR) is a measure of fertility, calculated by dividing the number of births in a given year by the number of women of reproductive age (usually 15-44 years) in the same year. This helps in understanding the fertility trends in a population.

**Why the Correct Answer is Right**
The correct denominator for GFR is the total number of women of reproductive age in the population. This is because GFR is an age-specific measure of fertility, which helps in identifying the fertility patterns in different age groups. The age range of 15-44 years is commonly used as it represents the typical reproductive age group for women. By using this denominator, the GFR can be calculated for different age groups, providing valuable insights into the fertility trends.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the GFR is not calculated using the total population. The denominator should be specific to the reproductive age group to accurately represent the fertility trends.

**Option B:** This option is incorrect because the GFR is not calculated using the number of women of childbearing age. While this term is often used interchangeably with reproductive age, it's not the standard term used in epidemiology.

**Option C:** This option is incorrect because the GFR is not calculated using the number of women in the population. This option might be confused with the Total Fertility Rate (TFR), which is a different measure of fertility.

**Clinical Pearl / High-Yield Fact**
When calculating GFR, it's essential to use the correct denominator to avoid misinterpretation of fertility trends. Remember that GFR is an age-specific measure, and using the correct denominator helps in identifying the fertility patterns in different age groups.

**Correct Answer:** C.