As Is True of the Gametophytes of All Land Plants

As is true of the gametophytes of all land plants, the gametophytes of true mosses lack stomata. Yet, the feather moss Pleurozium harbors nitrogen-fixing cyanobacteria. Which of the following is a feature of moss gametophytes that is most important for the continued survival of these cyanobacteria in the tissues of the feather moss gametophyte?

A) lack of cuticle
B) lack of vascular tissues
C) lack of true leaves or roots
D) lack of an independent sporophyte
E) lack of multiple cell layers in "leaves" of "buds"