Why Should One Expect the Soil's Nitrogen Not to Be

Why should one expect the soil's nitrogen not to be contained solely within the rhizoids of the Polytrichum mosses?

A) Rhizoids are associated with fungi that inhibit mineral transfer from soil to rhizoids.
B) Rhizoids are not absorptive structures.
C) Rhizoids consist of single, tubular cells or of filaments of cells.
D) Rhizoids lack direct attachment to the moss sporophytes.