**Core Concept**
The question is testing the understanding of a demographic indicator used to measure the rate of induced abortions in a population. This indicator is a key metric in public health and reproductive health research.

**Why the Correct Answer is Right**
The correct answer is the abortion ratio, which is a measure of the number of abortions performed per 100 live births in a given time period. This ratio provides a standardized way to compare abortion rates across different populations and time periods. The abortion ratio is calculated by dividing the number of abortions by the number of live births, and it is often expressed as a rate per 100 live births.

**Why Each Wrong Option is Incorrect**
* **Option A:** The abortion rate is a measure of the number of abortions performed per 1,000 women of reproductive age, not per number of live births.
* **Option B:** The general fertility rate is a measure of the number of births per 1,000 women of reproductive age, not a ratio of abortions to live births.
* **Option C:** The maternal mortality ratio is a measure of the number of deaths due to pregnancy-related complications per 100,000 live births, not a ratio of abortions to live births.

**Clinical Pearl / High-Yield Fact**
The abortion ratio is an important indicator of reproductive health and can be influenced by various factors, including access to contraception, abortion laws, and socioeconomic conditions.

**Correct Answer:** C.