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Which statements describe the decline of Sumer?

Choose all answers that are correct.

AThe swamps bred insects that carried disease.
BThe needed canals became too costly to build.
CThere was a lack of natural barriers that could discourage attack.
DAs the fields of Sumer grew saltier, harvests became smaller.

Verified Answer :

Sumer lacked a central army to defend them and their city-states. Instead they had local armies that protected each city-state, therefore making it easier for them to be invaded.