Answer:
decayed organic matter
Explanation:
Decaying organic matter is an important part of topsoil found worldwide.
Incorrect answers (with explanation):
Loam is a type of soil, not a part of topsoil.
Permafrost is only found in arctic regions, and is frozen ground, not a part of the soil.
Plant roots grow into topsoil, but are not a part of the soil itself.
I hope this helps!
