What did rivers contribute to the development of early civilizations? a. fertile land, irrigation, and transportation
b. fertile land, bathing area, and livestock supply
c. irrigation, trade, and defense against invaders
d. none of the above

Correct answer is a. fertile land, irrigation, and transportation .

Explanation:

A is the correct answer as around great rivers such as Tigris, Euphrates, Nile, Indus and many others civilization emerged due to fertile land that was created during the period when the rivers would overflow the land.

In addition to that they have improved irrigational system, so they could develop agriculture as a main labor during that period which brought them necessary crops.

Rivers were main way of transportation, which can be seen from many sources about Nile or Tigris.

All other answers are thus wrong.

an angle + its complement = 90 degrees