The Supreme Court Justified Its Decision to Strike Down the Use

The Supreme Court justified its decision to strike down the use of "white primaries" in the South by claiming that

A) the practice infringed on Congress's power to regulate interstate commerce.
B) parties were "an agency of the State," and therefore any practice of discrimination against blacks was a violation of the Fifteenth Amendment.
C) separate but equal elections violated the Fourteenth Amendment.
D) only Congress had the authority to conduct primaries under the Constitution.