Answer:
25 years
Step-by-step explanation:
Ossification is the process of bone tissue formation. Osteoblasts are responsible for the process of ossification. It begins when the fetus is three months old and goes on till 25 years of age. Upper limbs get ossified first, followed by lower limbs, sternum and vertebrae.
There are two types of ossification processes. When bone is directly developed using the primitive connective tissue (mesenchyme) it is called as intramembranous ossification, while in endochondral ossification cartilage is used as a precursor.