This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thorax, Subject name: Anatomy
Ribs develop from: 
Select and explain. 
A. Endothoracic fascia, B. Para-axial mesenchyme, C. Deep intercostal fascia, D. Superficial intercostal fascia
B: Para-axial mesenchyme
Answer: B: Para-axial mesenchyme 
Explanation: Ans. B Para-axial mesenchymeRef: Gray's Anatomy, 41st ed. pg. 212* The axial skeleton, vertebrae and ribs are derived from paraxial mesenchyme* The skull is derived from paraxial mesenchyme and neural crest mesenchyme* The skeletal elements in the limbs are derived from somatopleuric mesenchyme, which forms the limb buds.