How were the Maya able to establish a civilization even though they lacked river resources?

How were the Maya able to establish a civilization even though they latch River resources? ... the Mayans used astronomy hieroglyphics calendars number systems and built pyramids like the Egyptians and Mesopotamians. might have been the first people to use the number zero

Explanation:

Scholars have suggested a number of potential reasons for the downfall of Maya civilization in the southern lowlands, including overpopulation, environmental degradation, warfare, shifting trade routes and extended drought. It's likely that a complex combination of factors was behind the collapse.

the answers is b.   environments.