What is a term for a system with two or more governments exercising power over the same people and the same territory?

Which statement in the passage best reflects sumer's opinion of the dred scott decision? a."i speak what cannot be denied." b."[the] judgment was sustained by a falsification of history." b."the opinion was more thoroughly abominable than anything history." i speak what cannot be denied when i declare that the opinion of the chief justice in the case of dred scott was more thoroughly abominable than anything of the kind in the history of courts. judicial baseness reached its lowest point on that occasion. you have not forgotten that terrible decision where a most unrighteous judgment was sustained by a falsification of history. -charles sumner, 1865