A common element among all the river valley civilizations was:

irrigation systems that moved water to crops and settlements

developed plumbing systems

developed written materials

the worship of leaders as God's

A common element among all the river valley civilizations was irrigation systems that moved water to crops and settlements

Explanation:

River Valley civilizations where the civilizations that were found on the banks of the river like the Mesopotamia, Indus valley civilization. These civilization where agriculture based civilization as they depended on river for drinking water and irrigational activities