What Was the Aim of the 15th Amendment

What was the aim of the 15th Amendment?

A) to make it unlawful for registrars to apply unequal standards in voter registration procedures
B) to make it unlawful for registrars to reject applications because of immaterial errors
C) to extend the vote to former African American slaves without property
D) to extend the vote to former African American slaves and prohibit voter discrimination on the basis of race