Which Statement Describes the Critical Distinction Between Arbuscular Mycorrhizae and Ectomycorrhizae

Which statement describes the critical distinction between arbuscular mycorrhizae and ectomycorrhizae?

A) Ectomycorrhizae involve more penetration into root cells.
B) Arbuscular mycorrhizae often grow farther into soil and involve more penetration into root cells.
C) Arbuscular mycorrhizae form a mantle around root exteriors, whereas ectomycorrhizae only grow between root cells.
D) Arbuscular mycorrhizae are engaged in commensalisms, whereas ectomycorrhizae are engaged in mutualisms.