What Are Two Functions of Bone Marrow Stromal Cells with Respect

What are two functions of bone marrow stromal cells with respect to B-cell development?

A) Cytokine expression traps developing B cells in a specific location
B) Recruits macrophages to phagocytize self-recognizing B cells and decreases HSC when no active infection is present
C) Secretes release factors that direct the B cell to the spleen and expresses necessary cytokines
D) Traps developing B cells in a specific location and recruits red blood cells to bring oxygen to developing B cells
E) Triggers HSCs to produce more pro-B cells and secretes cytokines to stimulate osteoblast development