The correct option is A Establishment of Oligarchies
The Athenian coup of 411 BC was the result of a revolution that took place during the Peloponnesian War between Athens and Sparta. The coup overthrew the democratic government of ancient Athens and replaced it with a short-lived oligarchy known as The Four Hundred. Hence, Option A is correct. Among the rest of the options, monarchy could not be established because kings were overthrown, democracy could not be established since no women and not all adults had the right to vote. Hence, these are incorrect.