The correct effect of the Three-Fifths Compromise on Southern states is:
d. by allowing enslaved people to be counted as 3/5 of a person in southern states, it gave southern states more representation in congress.
The Three-Fifths Compromise was an agreement made during the Constitutional Convention in 1787 that determined how enslaved individuals would be counted for representation and taxation purposes. It allowed Southern states to count three-fifths of their enslaved population when apportioning representatives in Congress, which increased their political power relative to Northern states.