Answer:
C.
Explanation:
Reconstruction was an era of rebuilding the South and succeeding the era of the American Civil War. The Reconstruction era began in 1865 and lasted up to 1877.
The Reconstruction or rebuilding of the South failed due to many reasons but the chief among them was racism. During the Reconstruction era, there was a time of economic depression that led Northerners to step back from helping build the South that was destroyed during the Civil War.
From the given options the reason of failure of Reconstruction is not because of reintegration of Southern States into the Union. After the Civil War was over efforts were made to bring South in Union but because of poor Presidentship could not be enforced.
So, the correct answer is option C.