Final answer:
During B-cell maturation, bone marrow stromal cells signal to B cells, secrete IL-7, and provide a specialized microenvironment. The correct option is A.
Step-by-step explanation:
The bone marrow stromal cells perform the functions of signaling to B cells, secreting IL-7, and providing a specialized microenvironment during B-cell maturation.
1. Signaling to B cells: The bone marrow stromal cells release cytokines and growth factors that help stimulate the B cells to multiply and mature into antibody-producing plasma cells.
2. Secreting IL-7: IL-7 is a cytokine that promotes the survival and proliferation of B cells.
3. Providing a specialized microenvironment: The bone marrow stromal cells create a supportive environment that facilitates the development and maturation of B cells. The correct option is A.