The correct answer is C.
The Executive Order 9981 was enacted in 1948 by the US goverment leaded by President Harry Truman. It outlawed discrimination in the US Armed Forces based on race, color, religion or national origin motives. Therefore, it meant end of segregation in the military services.
This order precceded other landmark decisions related to the end of segregation, such as the one adopted by the US Supreme Court in 1954 in the case of Brown v. Board of Education, that led to the end of segregation in public education.