what general principle was established with the Plessy v. Ferguson Supreme Court decision?

a. States could not use taxes and literacy test to establish voting eligibility.
b. States could require separate facilities for African-Americans as long as the facilities were equal.
c. States could not prevent African-Americans from voting.
d. States could be punished with decreased Congressional representation if they did not allow African-Americans to vote.

b. States could require separate facilities for African-Americans as long as the facilities were equal.