What challenges faced by the South during Reconstruction under Radical Republicans?

Reconstruction (1865-1877), the turbulent era following the Civil War, was the effort to reintegrate Southern states from the Confederacy and 4 million newly-freed slaves into the United States. Under the administration of President Andrew Johnson in 1865 and 1866, new southern state legislatures passed restrictive “black codes” to control the labor and behavior of former slaves and other African Americans.

answer; (d) i believe that the correct answer is americans finally ran out of ammunition;

answer: this is because archeologists keep finding artefacts and ancient ruins dated more than 10000 to 15000 years, date around scientists said humans discovered language; which is at least mysterious as scientists always have said that is necessary to have a language to have architecture and some basic maths.

explanation: brainlest