You are presented with the question "Hydropower requires beavers damming what?" and the following answer choices: 
- lakes with large rocks
 - a hydraulic system
 - organisms and their habitat
 - streams with two branches
 - water with old boards
 - scarce resources
 - fissures of hot, acidic water
 - streams with fallen trees

Now knowing that hydropower requires damming a river and streams and rivers are crossed on rocks, beaver dams, on fallen trees or by wading, choose the best answer.


 

        streams with fallen trees 