Put the locations of origin, development, and action of lymphocytes in order

Lymphocytes are a type of white blood cells which occurs in the lymphatic system. Lymphocytes function to boost the immune system and there are two types: B cells and T cells. The B cells produce antibodies while the T cells destroy the body cells that have been taken over by microbes or that have become cancerous. Each lymphocyte is divided into left and right part.
1.The left side: the stem cells produces the precursors for lymphocytes.
2. Upper right: Lymphocyte precursors are processed to become T cells.
3. Lower left: processing of lymphocyte precursors to become B cells.
4. Lower right: lymphocytes are located in the lymphatic organs.

Covalent bond is the correct answer