Fact 1: Decomposition increases amount of organic matter in soil.

Fact 2: Dirt, soot or soil is easily distinguishable from mildew.

Given the two facts above, answer the question "What increases amount of organic matter in dirt?" with the following options: 
- animal transport
 - composure
 - composite
 - decomposition
 - chemical changes
 - fossil fuels
 - composition
 - nutrients


 

    decomposition     