Fact 1: Damming a river can cause a lake to form.

Fact 2: Beavers build dams that create ponds.

Given the two facts above, answer the question "What can be the cause of lakes and ponds forming?" with the following options: 
- beavers
 - heat
 - Pesticides
 - flooding
 - erosion
 - rainfall
 - loose soil
 - spring


 

 beavers        