why was the fifteenth amendment created?\nto prevent discrimination against voters based on race\nto prevent…

Brief Explanations:

The Fifteenth Amendment was part of the Reconstruction Amendments. It aimed to ensure that the right to vote could not be denied based on "race, color, or previous condition of servitude." This directly addresses preventing discrimination against voters based on race. The other options are incorrect. Preventing African - Americans from voting (opposite of the Amendment's intent), preventing Congress from extending voting rights (not the case as it was an extension itself), and preventing laws barring the African - American vote is too narrow as it's about prevention of discrimination in general (not just existing laws, but future discrimination too).

Answer:

To prevent discrimination against voters based on race