Republicans were responsible for the passage of the Thirteenth Amendment, which effectively nullified the Three-fifths Compromise. Why was this an issue of concern for Republicans?

A) because it meant that former Confederates were eligible to hold federal office

B) because it meant that the four million freed people in the South would now be counted in each Southern state's congressional appointment

C) because it "threw down the gauntlet" and threatened southern Democrats

D) because Lincoln opposed it.