Why did ancient civilizations develop in valleys of rivers such as the nile, indus, tigris and euphrates?

for the united states of america, 1945 to 1964 was a time of high economic growth and general prosperity. it was also a time of confrontation as the capitalist united states and its allies politically opposed the soviet union and other communist countries; the cold war had begun.

explanation:

they bring people together to achieve control of the government

basically choosinng what sets in   congress and presdicny this is to keepthe antion hole and so it can last because wiht out authority it wouldnt last a week