Final answer:
Before the Voting Rights Act of 1965, the percentage of eligible black voters who registered was very low, likely closest to 10%. After the Act, registration increased significantly, with Alabama seeing an increase from 19.3% to 51.6%. None of the provided options are correct.
Step-by-step explanation:
In Marion, Alabama, before the effects of the Voting Rights Act of 1965, the percentage of the eligible black voting population that registered to vote was extremely low due to disenfranchisement techniques like literacy tests and poll taxes. Given your options a) 10%, b) 25%, c) 40%, d) 50%, historical accounts and the context of the Voting Rights Act suggest that before the Act's passage, figures were considerably less than half, likely closer to 10% due to the stringent barriers to registration. However, after the passage of the Voting Rights Act of 1965, there was a substantial increase in voter registration among African Americans.
According to historical data, in Alabama, African American registration increased from 19.3 percent to 51.6 percent post the enactment of the Voting Rights Act. None of the provided options are correct.