Fact 1: The looseness of soil has a positive impact on a plant 's roots' growth in that soil.

Fact 2: Tree roots stabilize the soil and prevent soil erosion.

Given the two facts above, answer the question "what makes soil stable?" with the following options: 
- weather
 - heat
 - magma
 - rain
 - streams
 - water
 - trees
 - crust


 

       trees  