Question

why does an adult not have as many bones as a child?
osteoporosis leads to bone loss with age.
some separate bones gradually fuse with age.
many bones are replaced by cartilage with age.
bones are reabsorbed with age.
osteoclast activity overcomes osteoblast activity with age.

Explanation:

Children are born with more bones, around 300. As they grow, some separate bones gradually fuse together. For example, in the skull, several bones fuse over time. This is the main reason adults have fewer bones (206) than children. Osteoporosis is related to bone density loss in old - age, not the number of bones. Bones are not replaced by cartilage in a way that affects the number, and reabsorption and the balance between osteoclast and osteoblast activity are related to bone remodeling rather than the number of bones in the body.

Answer:

Some separate bones gradually fuse with age.