Answer:
c. literacy tests that prevent uneducated citizens from voting
Explanation:
Literacy tests were used in the voting system from the 1890s till 1960s. The purpose of this was to keep immigrants` votes away, mostly the ones by African Americans and immigrants from Eastern and Southern Europe. This test was a device for limiting immigrants` impact while not offending ethnic voters.
The Voting Rights Act was signed into law by President Lyndon Johnson on August 6, 1965. In that way, literacy tests implemented by Southern states after the Civil War were outlawed.