Final answer:
W.E.B. Dubois believed that the problem of the 20th century was the color line, or racial discrimination and inequality. This statement was proven true through various historical events and struggles throughout the century.
Step-by-step explanation:
W.E.B. Dubois famously stated that the problem of the 20th century was the color line, referring to the racial divide and discrimination between black and white individuals. He believed that racism and inequality were the main challenges faced by people of African descent around the world.
This statement by Dubois was proven true throughout the 20th century through various historical events and struggles. The civil rights movement in the United States, apartheid in South Africa, and the struggle for decolonization in Africa are just a few examples of how racism and inequality persisted and were fought against during this time period.