The best and most correct answer among the choices provided by the question is the sixth choice. One of the reason of the decline of the empire is violence, and the best example of which is the assassination of Julius Caesar. I hope my answer has come to your help. God bless and have a nice day ahead!
It would be the "Bill of Rights" that lists some of the rights and liberties of the people and of the state, since the Anti-Federalists insisted on including this section in order to make sure that the government did not become tyrannical.