The South's Move from Voting for the Democratic Party to Voting

The South's move from voting for the Democratic Party to voting for the Republican Party in the 1960s was the result of

A) 18-year-olds winning the right to vote through the ratification of the Twenty-Sixth Amendment.
B) Cuban immigrants becoming a larger share of citizens living in southern states.
C) white southerners' opposition to the Democratic Party's integrationist racial policies.
D) black southerners' support of the Republican Party's willingness to support tax cuts and increased military spending.