Final answer:
c. Energy conservation is the factor that best allows humans to utilize water as a resource.
Step-by-step explanation:
The factor that best allows humans to utilize water as a resource is c. energy conservation. Energy conservation refers to the practice of using energy efficiently and minimizing waste. By conserving energy, humans can reduce their water usage and ensure the sustainability of water resources.
For example, using energy-efficient appliances and fixtures that require less water can help in water conservation efforts.