Why did korea choose to isolate itself in the 1500s

Because the country saw this isolation as a way of defending itself against foreign invasions and because they believed that its culture was superior.

Explanation:

Before being divided into two countries, chorea had already been isolated from the world in 1500 during the Choson dynasty. This isolation was made as a strategy of getting rid of foreign invasions (especially those made by China and Japan) and a way to protect the superiority of the Confucian culture.

you didn't list the options. however, a few communist countries today are: the people's republic of china, north korea, and cuba.