Final answer:
World War II was a catalyst for the spread and evolution of black popular music, as it opened new opportunities and aided in the dissemination of jazz and blues through advancements in technology. The correct option is c.
Step-by-step explanation:
The impact of World War II on black popular music was significant, leading to the genre's spread and evolution. Far from leading to a decline, the war helped disseminate jazz and blues by creating new opportunities for African American musicians. This occurred both due to the need to fill entertainment spots left by those who went to fight and by the changes in society that the war induced. As African American men and women moved into new jobs, including those in the entertainment industry, the dispersion of their music increased.
Furthermore, the social changes brewing at this time helped set the stage for the Civil Rights Movement, during which music played a key role in expressing and shaping African American identity. Technology allowed music to be recorded and widely distributed, which was a boon for genres like jazz and blues, as it allowed them to transcend local boundaries.
Subsequently, the post-war period saw a great increase in the popularity of black popular music, setting the stage for future genres like rock 'n' roll to flourish, inspired by and incorporating elements of this music.
Hence, Option c is correct.