The Degradation of Irrigated Soils Across the Once Very Productive

The degradation of irrigated soils across the once very productive "Fertile Crescent" of the Middle East was due primarily to _____.

A) high calcium and magnesium levels in the irrigation waters
B) high levels of calcium-containing salt in the irrigation water
C) inadequate equipment and power to properly cultivate the soil
D) poor internal drainage of the soils
E) destructive wars in the region