The cells responsible for bone resorption are
osteoclasts
osteoblasts
fibroblasts
osteocytes

osteoclasts

Explanation:

Osteoclast is a cell that makes up the bone matrix, quite large compared to other cells, multinucleated, and is involved in resorption and remodeling of bone tissue. It has a lysosome-rich cytoplasm, numerous mitochondria, and a highly developed Golgi complex.

Although it was once believed that osteoclasts came from osteoprogenitor cells, they are now known to come from bone marrow derived from coalescent monocytes.

c. would be the answer : )

explanation:

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.