Why is the stroma important in hematopoiesis?

id like to answer it as: B) The stroma serves as the supporting tissue for developing cells.

Stromal tissues within hematopoietic organs play a key
role in the regulation of hematopoiesis. The stroma provides
structural support for hematopoiesis by formation of a
network of connective tissues. They also define a
microenvironment suitable for maintenance of HSC as well
as providing cues for development of all hematopoietic
lineages.

Source: ResearchGate; The Role of Stroma in Hematopoiesis and Dendritic Cell Development;
Geneviève Despars†, Jonathan Tan, Pravin Periasamy and Helen C. O’Neill; 2007