Answer:
Founded in 1865, the Ku Klux Klan (KKK) extended into almost every southern state by 1870 and became a vehicle for white southern resistance to the Republican Party’s Reconstruction-era policies aimed at establishing political and economic equality for Black Americans. Its members waged an underground campaign of intimidation and violence directed at white and Black Republican leaders. Though Congress passed legislation designed to curb Klan terrorism, the organization saw its primary goal–the reestablishment of white supremacy–fulfilled throughDemocratic victories in state legislatures across the South in the 1870s. After a period of decline, white Protestant nativist groups revived the Klan in the early 20th century, burning crosses and staging rallies, parades and marches denouncing immigrants, Catholics, Jews, African Americans and organized labor. The civil rights movement of the 1960s also saw a surge of Ku Klux Klan activity, including bombings of Black schools and churches and violence against Black and white activists in the South.
Explanation:
From what I can recall, the Adams-Onis Treaty more or less gave Florida to the U.S. but it did not exactly end the Second Seminole War, which can be made obvious with the fact that there are Seminoles still living in Florida. I don't remember the Treaty having anything to do with the British since this treaty was between Spain and the U.S.
Basically, I believe the answer is B.