South korea’s economic success resulted in

the growth of a middle class
a large gap between rich and poor
the development of nuclear power
a trade network with north korea

the growth of a middle class

Explanation:

South Korea experienced an economic transformation between 1975 and 1999. In that period, agriculture went from occupying 45.7% of the active population to 11.6% and currently represents only 3.0% of GDP. After the Korean War, US and Japanese investments, skilfully directed by the Korean Government to strategic sectors, allowed an economic takeoff that has led the country to overcome countries like Spain in GDP in terms of PPP. Today, South Korea is the 11th largest economy (by GDP PPP) in the world, and is classified as a developed country by the UN, the World Bank and the International Monetary Fund (IMF).

letter d is correct.

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