Development is the process of improving the material conditions of people in a nation. a nation's development level is based on the united nation's human development index which focuses on economic, social, and demographic development as well as the gdp.

A nation’s development level is based on the United Nation’s Human Development Index (HDI), which focuses on economic, social, and demographic development. More specifically, the HDI focuses on a nation’s gross domestic product (GDP) for economics, literacy rates and education for social factors, and life expectancy for demographics. A country's gross domestic product is the total market value of all officially recognized final goods and services produced within a country in a year. GDP per capita is often considered an indicator of a country's standard of living.

answer; (d) melting of sea ice;