What natural resource did the Mesopotamians use to protect their cities from floods? trees
reeds
stone walls
mud bricks

Mud Bricks

Explanation: Fertile Crescent has important natural resources that encourage settlement including Mud

when [oh-] is 10-5  m, and [h3o+] is 10-9  m, the poh is 5 and ph is 9. again in both cases the sum of ph and poh is 14. however, the hydrogen ion concentration is not always going to be equal to exactly 1 x 10 raised to a negative number. for example, we skipped over the value of 2.0 x 10-7.

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