What Factor Contributed to the Transition from the Fifth to the Sixth

What factor contributed to the transition from the fifth to the sixth party system?

A) the election of Franklin Roosevelt as president
B) Democratic candidates and party leaders, particularly outside the South, came out against the "separate but equal" system of racial discrimination.
C) the end of World War II
D) Party machines, run by Democrats in urban areas, could no longer control the flow of political information with the rise of television.
E) the election of Ronald Reagan as president