By the end of the civil war
a. many confederate leaders had been tried for treason
b. african americans had gained full citizenship
c. the south's economy had been destroyed
d. congress had passed legislation to rebuild the nation

I'm pretty sure it is C Reasoning: It's not A because most Confederate leaders were pardoned. It's not B because after the civil war, the South was forced to give citizenship to all Blacks. It's not D because this too was during the reconstruction period after the civil war.