**Core Concept**
The death rate is a measure of mortality in a population, expressed as the number of deaths per 1,000 people per year. It is an important demographic indicator used to assess the health status and mortality patterns of a population.

**Why the Correct Answer is Right**
The death rate is best demonstrated by the crude death rate (CDR), which is calculated as the total number of deaths in a population divided by the total population multiplied by 1,000. This rate provides a general idea of the mortality rate in a population and is useful for comparing mortality rates between different populations.

**Why Each Wrong Option is Incorrect**
* **Option A:** The birth rate is a measure of fertility, expressed as the number of live births per 1,000 people per year. It is not a measure of mortality.
* **Option B:** The infant mortality rate is a specific measure of mortality, but it only applies to children under 1 year of age and is not a general measure of mortality.
* **Option C:** The life expectancy at birth is a measure of the average number of years a person is expected to live, but it does not directly measure mortality.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the crude death rate is influenced by various factors, including age structure, population growth rate, and the quality of vital statistics. Therefore, it's crucial to consider these factors when interpreting and comparing mortality rates between different populations.

**Correct Answer: C.**