Final answer:
Spherocytes are not a sign of RBC regeneration but are typically associated with hemolytic anemia. Nuclear remnants, polychromasia, and anisocytosis with macrocytosis are signs of increased RBC production. Macrophages assist in the maturation of RBCs, and hematopoiesis predominantly takes place in the bone marrow.
Step-by-step explanation:
The option that is not a sign of red blood cell (RBC) regeneration is C. Spherocytes. Spherocytes are not indicative of new RBC production; rather, they are typically associated with hemolytic anemia. On the other hand, A. Nuclear remnants (like Howell-Jolly bodies), B. Polychromasia (a sign of reticulocytes, which are immature RBCs), and D. Anisocytosis with macrocytosis (variation in RBC sizes with some larger than normal) can all be indications of increased RBC production as the bone marrow responds to anemia or blood loss.
Macrophages play a role in the maturation of a red blood cell by helping to remove the nucleus and organelles from developing RBCs in a process called erythrophagocytosis.
Hematopoiesis, the process of blood cell production, occurs mainly in the B. bone marrow. Granulocytes are a type of D. leukocyte (white blood cell), which are important for the body's immune response. Aging and damaged erythrocytes are removed from the circulation primarily by c. macrophages.