Which was part of Sumerian farming and trading? Select all correct answers. A: Levees held back the annual floods of the Tigris and Euphrates Rivers.

B: Lumber, stone, and gold produced in Sumer could be traded for food.

C: Surplus barley and wheat could be traded for other things

C and B

Explanation: I took a test with this question.

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crop rotation kepy different plants in the soil instead of once constintly. when switching out plants you have different nutrients being absorbed at different speeds and different roots growing differently therfore the spoil and water flow have to adapt and carry fresh nutrients to carry the constant changes that were going on in the soil.