Answer:
Secret ballots.
Explanation:
Secret ballots is where people can vote anonymously, since there were many problems with blackmailing and vote buying within the system.
No one will be able to help you based on this picture. This is simply too obscure.
B, when people controlled the flow of the rivers.
The problem with mesopotamia was that although it had incredible natural defenses, it was in the middle of an enormous flood plain, so the people needed a way to control how much water came in and out of the farmlands.