The correct answer is A. They began near rivers because they had developed complex trade networks.
The first great civilizations in the history of humanity were born alongside great rivers. This is the case of Mesopotamia, between the rivers Tigris and Euphrates, where around six thousand years ago flourished the Sumerian, Akkadian, and Babylonian civilizations; India that developed alongside the Indo and Ganges rivers; China that flourished near the Yangtze river; and Egypt, that emerged alongside the Nile river.
They all developed near big rivers because rivers allowed very productive agriculture, which permitted the population to settle and to produce a surplus of resources, giving place to the rise of the first cities. At the same time, this surplus allowed to exchange goods with other settlements near the river and, therefore, commerce was born in these rivers, which were used as a way to transport goods between the cities. This way, rivers became the basis of complex trade networks that shaped the first great civilizations of History.
