Which of the following best explains how and why the practice of native american slavery changed over time? a. over time, native americans replaced african slaves because they were better at farming and mining for gold. b. over time, native american slaves replaced african slaves because of the high taxes on the african slave trade. c. over time, native american slaves were replaced by african slaves because the native americans were dying of diseases. d. over time, native american slaves were replaced by african slaves because of treaties signed between the europeans and the native americans.