Why did American consider world war 1 to be a significant event by the wars end

The entry of the United States was the turning point of the war, because it made the eventual defeat of Germany possible. It had been foreseen in 1916 that if the United States went to war, the Allies' military effort against Germany would be upheld by U.S. supplies and by enormous extensions of credit.

Explanation:

  b.

there are isolated pockets of farming, generally around rivers and oases, which are used for irrigation.