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

Fact 2: Beavers build dams.

Given the two facts above, answer the question "What can cause lakes to form?" with the following options: 
- flooding
 - loose soil
 - rainfall
 - break off
 - heat
 - erosion
 - Beavers
 - spring


 

       Beavers  