The correct answer is A. Per capita income (PCI).

Per capita income is the average income earned by each person in a given area, such as a country or a region.

It is calculated by dividing the total income of the area by its population.

Per capita income is a good measure of the standard of living because it reflects the average purchasing power and well-being of the people in the area. It also allows for easy comparison across different areas and over time.

Per capita income is different from gross domestic product (GDP), gross national product (GNP), and net national income (NNI), which are other measures of economic output.

GDP is the total value of goods and services produced within a country’s borders in a given period.

GNP is the total value of goods and services produced by the residents of a country, regardless of where they live, in a given period.

NNI is the total income earned by a country’s residents, minus the depreciation of capital assets, in a given period.

These measures do not account for the size or distribution of the population, and therefore do not accurately reflect the standard of living of the average person.