Final answer:
The primary significance of the rivers in 'A Negro Speaks of Rivers' is their ancient and timeless nature, symbolizing the endurance and resilience of African Americans.
Step-by-step explanation:
In Langston Hughes's poem 'The Negro Speaks of Rivers', the primary significance of the rivers is their ancient and timeless nature. The speaker of the poem associates themselves with these rivers, expressing a deep connection to the history and culture of African Americans. The use of rivers as a metaphor highlights the endurance and resilience of the African American people throughout history. Thus, option b.) The ancient rivers have survived, is the correct answer.