Where and when do primary and secondary ossification centers form in long bones?

• A. Primary centers form in the diaphysis during fetal development; secondary centers form in the epiphyses after birth; growth plates remain between until maturity.
• B. Primary centers form in the epiphyses after birth; secondary centers form in the diaphysis during fetal development.
• C. Primary centers form in the metaphysis after birth; secondary centers form in the periosteum during childhood.
• D. Both centers form after puberty in response to growth spurts.

Answer: (A)