Final answer:
The growth of the four major ancient civilizations was supported by rivers, which allowed for sustainable agriculture, leading to population growth, specialization of work, and the development of governments. The correct option is b.
Step-by-step explanation:
The growth in all four of the major civilizations studied was supported primarily by rivers. Rivers were crucial for these civilizations because they provided a consistent and reliable source of water for agriculture, which was the foundation of stable, settled societies.
The ancient civilizations of Africa, Europe, Asia, and the Americas all experienced significant growth due to the agricultural surplus that rivers made possible.
This led to an increase in population, the rise of specializations like traders, builders, and artists, and the establishment of complex social structures and government systems. The correct option is b.