Which was not a reason the north began to lose interest in the southern reconstruction by the early 1870s?

a. southern intransigence was increasingly frustrating to the north, whose soldiers had fought for blacks' freedom.
b. the violence in the south was increasingly disturbing and seemed to indicate that blacks would never really be free.
c. other issues, such as indian wars, western expansion, and others started to overtake northerners' attention.
d. real and propagandized evidence of corruption in the reconstructed southern governments discouraged the north.