Final answer:
The red bone marrow is responsible for the production of all formed elements of human blood including erythrocytes, leukocytes, and platelets through the process of hematopoiesis. The correct option is a.
Step-by-step explanation:
All of the categories of formed elements of human blood, which include erythrocytes (red blood cells), leukocytes (white blood cells), and platelets (thrombocytes), are produced by the red bone marrow. Hematopoiesis is the process through which these formed elements are continually produced, with stem cells differentiating into myeloid and lymphoid lineages.
While the red bone marrow is the primary site for hematopoiesis, certain stages of cell differentiation may take place in other organs, such as the maturation of B cells in the marrow and T cells in the thymus.
In the case of conditions like bone marrow failure, the liver and spleen may take over some of these functions in a process known as extramedullary hemopoiesis. It's also essential to know that the yellow bone marrow stores fat and does not produce blood cells, and the thymus is mainly involved in the maturation of T cells after they have left the bone marrow. Hence, a is the correct option.