The correct answer is states were giving literacy tests to some voters to keep them from qualifying to vote.
The literacy tests implemented, especially in Southern states, were a tactic used by white Southerners to stop African Americans from voting. These tests were usually extremely difficult to pass. Along with this, the origins of these tests show why they were targeted at African Americans.
After African Americans were able to vote thanks to the 15th amendment, many Southern states created literacy tests. The Southern governments knew that a vast majority of African Americans would not pass, since many states made it illegal to teach blacks how to read.