Question

Which was one major achievement of the civil rights movement during the 1940s or 1950s?

Answer 1

B. Brown v. Board of Education.
Racial segregation based upon "separate but equal" were desegregated and deemed unconstitutional in the 1950s.

Answer 2

I believe the answer is: B.The Brown v. Board of Education ruling

In that ruling, the supreme court ruled that separating schools based on skin colour is deemed as unconstitutional because it specifically violates  the 14th amendment, which states that minorities who had been freed from slavery in the past is guaranteed with citizenship rights and equal protection/treatment under the law.