Final answer:
Life expectancy is relevant to economic growth primarily because it is an indicator of the overall health of a nation's citizens, leading to higher productivity and standards of living.
Step-by-step explanation:
Life expectancy is relevant to economic growth because it reflects the overall health and productivity of a nation's citizens. Higher life expectancy often correlates with a stronger, more stable economy. This is because healthy populations tend to be more productive, with higher quality healthcare and lower birth rates contributing to higher standards of living. Additionally, a greater life expectancy can mean a larger proportion of the population is able to work for a longer period, thus contributing to the economy for more years. This links to higher levels of GDP per capita, which indicates both productivity and the standard of living in a country.
However, when it comes to the choices provided in the question, option A, 'It is an indicator of the overall health of a nation's citizens,' is the most accurate. While higher life expectancy does often lead to greater economic prosperity, the other options are less directly tied to economic growth or may be misconceptions about older populations and economic contributions.