These cells are capable of cell division and mature into bone-forming cells:

Osteoprogenitor cells are the correct answer because they are the stem cells that are responsible for the generation of osteoblasts, which are the cells that form bone. These osteoprogenitor cells have the ability to undergo cell division (mitosis) and differentiate into osteoblasts when stimulated by certain factors in the body. This is a crucial process in bone development, growth, and healing.

In contrast, chondrocytes are involved in cartilage formation and do not directly contribute to bone formation. Osteoblasts are the actively metabolizing bone-forming cells, but they do not divide; once they are formed from osteoprogenitor cells, they begin to synthesize bone matrix. Osteocytes are matured osteoblasts that have become embedded in the bone matrix; they maintain bone tissue but do not have the capacity to divide or directly form new bone. Thus, osteoprogenitor cells are essential for the generation of new osteoblasts, making them pivotal in the process of bone formation.