Hiram Rhodes Revels was a key figure during the Reconstruction era because
A) he was a co-founder of the Ku Klux Klan.
B) he helped to dismantle the early formation of the Ku Klux Klan.
C) he was the chief prosecutor in the impeachment trial of Andrew Johnson.
D) he was the first African-American elected to a seat in the U.S. Congress.