Why was black Wall Street so important to the former enslaved blacks

Greenwood was home to a thriving Black commercial district, whose many red brick buildings belonged to Black Americans and housed thriving businesses, including grocery stores, banks, libraries, and much more; one of the most affluent African-American communities in the country, leading to the nickname, "Black Wall"

oil! is what i am assuming

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