What resources most directly led to the development of early civilizations in river valleys?

The first civilizations that we have knowledge of developed in the valleys of major rivers: the Nile (Egypt), the Tigris and the Euphrates (Mesopotamia), the Yellow River (China) and the Indus River (India).

These civilizations developed in the valleys of rivers because this environment provided them with various vital resources. A constant and reliable source of water was needed for the development of agriculture, which allowed them to sustain large populations. Agriculture also flourished due to the fertile soil that tends to surround river valleys. The rivers also worked as a highway, allowing them to develop trade and facilitating the exchange of information.

norsemen from northern countries had made earlier journeys

either b) they were often feared and despised by other native cultures. or

c) their obsession allowed them to coexist with many other native cultures because of their peaceful nature.