Please give explanation when answering

B - setting up the sharecropping system

Explanation:

Voting for Hiram Rhodes Revels was an African congressman, so wealthy Southerners who would want to keep cheap labor on plantation through African-American slaves wouldn't vote for him.

The Jim Crow laws helped Southerners continue segregation, keeping them wealthy, so they wouldn't oppose them.  

The Freedmen's Bureau was established by Congress to millions of blacks gain free lives after the Civil War, meaning wealthy Southerners wouldn't keep their cheap labor. Southerners would want to keep the cheap labor, so they wouldn't fund that.

Therefore, sharecropping is the only one left that makes sense because it kept slaves dependent on their landowners/masters to pay for their food, rent, and any way of making money. The wealthy plantation owners of the South would want slaves to be dependent on them for their life so they could keep their cheap labor. This would be how they resisted Reconstruction.