This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
The precailagenous analog to bone arises from? 
Select and explain. 
A. Ectoderm, B. Endoderm, C. Mesenchyme, D. Mesoderm
C: Mesenchyme
Answer: C: Mesenchyme 
Explanation: There are two major modes of bone formation, or osteogenesis, and both involve the transformation of a preexisting mesenchymal tissue into bone tissue. The direct conversion of mesenchymal tissue into bone is called intramembranous ossification. This process occurs primarily in the bones of the skull. In other cases, the mesenchymal cells differentiate into cailage, and this cailage is later replaced by bone. The process by which a cailage intermediate is formed and replaced by bone cells is called endochondral ossification Ref:Inderber singh Embryology.