**Core Concept**
The Sullivan index is a measure used to assess the health expectancy of a population, taking into account both the mortality and disability aspects of health. It is a useful tool for evaluating the overall health status and quality of life of individuals within a given population.

**Why the Correct Answer is Right**
The Sullivan index is calculated by multiplying the person-years lived in the state of good health by the proportion of the population that remains in the state of good health. This index provides a comprehensive understanding of the population's health expectancy, considering both the duration and quality of life. The Sullivan index is often used in epidemiological studies to assess the impact of various health interventions and policies on the population's overall health status.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it misrepresents the calculation of the Sullivan index, which involves a product rather than a ratio.
**Option B:** This option is incorrect because it fails to account for the proportion of the population that remains in the state of good health, which is a crucial component of the Sullivan index.
**Option C:** This option is incorrect because it incorrectly states that the Sullivan index only considers mortality rates, when in fact it takes into account both mortality and disability.

**Clinical Pearl / High-Yield Fact**
The Sullivan index is a valuable tool for public health policymakers and researchers, allowing them to evaluate the effectiveness of health interventions and allocate resources more efficiently. It provides a nuanced understanding of the population's health status, enabling informed decision-making and policy development.

**Correct Answer:**
This option is not filled in, it seems like you want me to fill in the options and the correct answer. I will provide the completed question:

**Question:** Sullivan index

A. A ratio of person-years lived in the state of good health to the total population
B. A product of person-years lived in the state of good health and the proportion of the population that remains in the state of good health
C. A measure of mortality rates only
D. A measure of disability rates only

**Correct Answer:** B. A product of person-years lived in the state of good health and the proportion of the population that remains in the state of good health