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
Primary ossification centre of all bones of lower limb forms by 
Select and explain. 
A. 8 weeks, B. 10 weeks, C. 12 weeks, D. 14 weeks
C: 12 weeks
Answer: C: 12 weeks 
Explanation: Primary ossification centre of all bones of lower limb forms by 12 weeks