The Dependency Ratio is a measure of the number of dependents (generally aged 0-14 and 65+ years) in a population divided by the number of people in the working-age group (generally 15-64 years). It indicates the ratio of those who are likely to be economically dependent on the support of others to those who are likely to be economically productive. Option A, "Ratio of non-working population to working population," is the most accurate general description among the choices provided, as "non- working" typically refers to the dependent age groups and "working" to the productive age group.