Which of the following steps of intramembranous ossification is correct ?

1. clusters of oestoblasts from oestoid that becomes mineralized
2. oesteoblasts differentiate within mesenchymal connective tissue
3. spicules of bone radiate out from the ossification centers
4. mesenchymal cells aggregate

A. 4,1,2,3

B. 1,2,4,3

C. 4,2,1,3

D. 4,3,2,1