The correct answer here would be C. The usual story goes that Confederation Congress only assigned them to propose the amendments to the Articles but instead they created an entirely new document. This is their reason, among others but none of them are correct as the Convention did not exceed its authority. The Confederation Congress for one was not a government in the true sense of the word. It was more an alliance like NATO. The convention was a also a meeting about just more than the Articles. The convention was beyond the Congress and its opinion was nothing more than that, just an opinion. Furthermore all 13 states ratified the Constitution. So no the Convention did not exceed its authority.
1. it stopped the spread of slavery north of the Ohio river
I think that the answers are A., C., E.,
