Answer:
The correct answer is D) Blood cells.
Haematopoiesis is the process by which cellular components of the blood are formed from multi-potent haematopoetic stem cells.
In developing embryo, formation of blood cells can take place in spleen, liver and lymph nodes but it takes place in bone morrow once it is completely developed.
However, maturation and activation of some lymphocytes can take place in different organs such as thymus, spleen, and lymph nodes.
Haematopoetic stem cells divide and differentiate into myeloid and lymphoid progenitor cells which further divide and differentiate into various types of blood cells (RBC, lymphocytes and myeloid cells).