The correct answer is: a) Gross National Income (GNI) per capita.
Gross National Income (GNI) per capita is a measure of a country’s economic output per person. It is calculated by dividing a country’s gross national income (GNI) by its population. GNI is the total value of all goods and services produced in a country in a year, plus net income from abroad.
GNI per capita is a good indicator of a country’s standard of living because it takes into account both the size of a country’s economy and the number of people living in that country. A higher GNI per capita indicates that a country’s economy is larger and that its people are generally wealthier.
The other options are not good indicators of a country’s standard of living. The number of luxury cars in a country does not necessarily reflect the wealth of its people, as some people may own multiple luxury cars while others may own none. Celebrity sightings are also not a good indicator of a country’s standard of living, as celebrities often live in countries that are not their home countries. Happiness surveys are also not a good indicator of a country’s standard of living, as people’s happiness can be influenced by factors other than their economic well-being.