function of bone marrow b cell development

What are two functions of bone marrow stromal cells with respect to B-cell development?
   
A.   Traps developing B cells in a specific location and recruits red bloods to bring oxygen to developing B cells
B.   Triggers HSCs to produce more pro-B cells and secretes cytokines to stimulate osteoblast development
C.   Secretes release factors that direct the B cell to the spleen and expresses necessary cytokines
D.   Cytokine expression and traps developing B cells in a specific location
E.   Recruits macrophages to phagocytize self-recognizing B cells and decreases HSC when no active infection is present