3. How did southern states respond to the ratification of the 15th Amendment? A. By forcing African Americans to work as tenant farmers and sharecroppers.
B. By imposing requirements designed to deny African Americans the right to
vote.
C. By creating a segregated public education system
D. B By shutting down all remaining offices of Freedmen's Bureau

B. By imposing requirements designed to deny African Americans the right to  vote.

Explanation:

The 15th Amendment essentially gave black Americans the right to vote as it outlawed the denial of voting rights based on color, race or previous condition of servitude. The Southern States however, found a way to get around this by imposing requirements designed to deny blacks the right to vote.

Some of these included literacy tests and poll taxes. Most black people did not have access to adequate education in the southern states so when literacy tests were introduced as a requirement for being able to vote, they could not make the cut.

Poll taxes required that blacks pay a tax to vote. Whites were excluded from this if their grandfathers voted in an earlier election, something blacks did not qualify for as they had only recently gotten the right to vote.