As a long bone develops, the point where osteoblasts first replace calcified cartilage with spongy bone becomes the from which further development proceeds.

a) primary ossification center

b) metaphysis

c) periosteum

d) secondary ossification center

e) epiphyseal line

A) primary ossification center

Explanation:

Endochondral ossification refers to the gradual replacement of a cartilage model with a bone. The primary ossification center represents the region where bone tissue gradually replaces most of the cartilage model. The deposition of the bone extracellular matrix over the remnants of calcified cartilage is done by osteoblasts. It results in the formation of spongy bone trabeculae. Primary ossification spreads from the central location toward both ends of the cartilage model.

substitution is the answer in this case

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