Final answer:
The NAD allowed Black Deaf people to join following World War II, a period of significant change and civil rights activism spurred on by the contributions of African Americans to the war effort and the return of Black soldiers demanding equality.
Step-by-step explanation:
The event that preceded the National Association of the Deaf (NAD) allowing Black Deaf people to join the organization was B. World War II. During World War II, African Americans filled many jobs left vacant by those who went off to fight in the war, which included working in the defense industries. African American soldiers returning from service brought with them a determination to have equal rights, which led to increased civil rights activism. Also, movements like the "March on Washington Movement," executive orders like 8802, and the creation of bodies such as the Fair Employment Practice Committee (FEPC) contributed to a social landscape where organizations, including the NAD, felt pressured to open their doors to African Americans.