Answer the following question given this paragraph: 

Water is recycled constantly through the ecosystem. That means any water you drank today has been around for millions of years. You could be drinking water that was once drunk by George Washington, the first humans, or even the dinosaurs.


Q: Water is recycled constantly through which system?

 Choices:

- the hydropshere

- the habitat

- the troposphere

- the ecosystem

A:
the ecosystem
