Answer:
The correct option is: (A) stem cells
Explanation:
The bone marrow is a semi-solid tissue which is generally found in the spongy portions of the bones. In the bone marrow, all the blood cells are produced from the unspecialized precursor cells, which are known as the stem cells. Firstly, the stem cells divide and form the immature blood cells. These immature blood cells then further divide and mature to form the mature blood cells.
Therefore, the stem cells are the precursor cells which transform and mature to form the blood cells.