Why were river valley civilizations called "the cradles of civilization"?

These were the first civilizations to exist. Most early civilizations were polytheistic.

Explanation:

Mesopotamia, the area between the Tigris and Euphrates Rivers (in modern day Iraq), is often referred to as the cradle of civilization because it is the first place where complex urban centers grew.

the indians crossed artificial boundaries, setting the stage for conflict

john maynard keynes developed new economic theories in response to the : b) great depression of the 1930s. his theories are so important that they are known as "keynesianism". in his works he supports the idea of a government with deeper involvement and intervention to end the great depression.