Answer:
<u>A common element among all the river valley civilizations was irrigation systems that moved water to crops and settlements</u>
Explanation:
- <u>River Valley civilizations where the civilizations that were found on the banks of the river like the Mesopotamia ,Indus valley civilization.</u>
- <u>These civilization where agriculture based civilization as they depended on river for drinking water and irrigational activities</u>
Theory because a theory has to be backed up by several experiments
The answers are
1. nitrogenous
2. acid-base
3. fluid
B!!!!!!!!!!!!!!!!!!!!!!!!!!
The answer is A because they need the sunlight to go through the water
