For intramembranous ossification to take place, which of the following is necessary?
a) an ossification center forms in the fibrous connective tissue.
b) a medullary cavity forms.
c) a bone collar forms around the cartilage model.
d) the cartilage matrix begins to deteriorate.

An ossification center forms in the fibrous connective tissue.

Explanation:

Intramembranous ossification is an important process of formation of bone from the fibrous membrane. This process occur during the the fetal development.

Mesenchyme stem cell in the meduallry cavity starts the process of intramembranous ossification. The important process during intramembranous ossification is the formation of ossification center in the fibrous connective tissue.

Thus, the correct answer is option (A).

the calvin cycle takes place in the stroma of the chloroplast. carbon dioxide enters the stroma of the chloroplast to combine with the five-carbon compound called ribulose1, 5-biphosphate to form two molecules of a three-carbon compound called 3-phosphoglyceric acid. this reaction is catalyzed by an enzyme called ribulose bi-phosphate carboxylase.