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

Fact 2: Soil or dirt is typically high in silica and alumina.

Given the two facts above, answer the question "What has a positive impact on root growth in dirt?" with the following options: 
- nutrients
 - burrs
 - exercise
 - support
 - evaporation
 - looseness
 - Sand dollars
 - sun's heat


 

      looseness   