Despite the Tendency of Newly-Enfranchised Black Voters in the South

Despite the tendency of newly-enfranchised black voters in the South to support Republican candidates in the years following the Civil War, why did the South become a Democratic stronghold?

A) Most of these new black voters moved to northern states.
B) Most Southern blacks did not have the time to devote to political participation.
C) Southern Democrats tended to align more with Republicans than with the rest of the Democratic Party.
D) Southern white Democrats found ways to keep blacks from voting.
E) There were just too few blacks in the South.