Final answer:
B cells follow both CCL19 and CCL21 chemotactic signals to migrate to the cortical regions of secondary lymphoid tissue.
Step-by-step explanation:
B cells follow both A and C chemotactic signals to migrate to the cortical regions of secondary lymphoid tissue.
The chemotactic signals that attract B cells are CCL19 and CCL21.
These chemokines are produced by stromal cells and attract B cells through a process called chemotaxis.
Once the B cells reach the cortical regions, they interact with other immune cells to initiate an immune response.