The answer to the fill in the blank question is option D) Democracy
All through the 1970s and 1980s the African continent suffered from regional rivalries, military dictatorships and autocratic governments. All these were backed by either Soviet Union or the United States who used the countries for their proxy wars.
By the 1990s, as the cold war ended, many African nations embraced change, gave up their past systems and started to gradually move towards democracy.