This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Orthopaedics
True about Atlanto-axial joint 
Select and explain. 
A. Vertebral artery passes posterior to foramen magnum, B. Atlanto-occipital joint has flexion and extension movement, C. Posterior longitudinal ligament does not pass through the spinal canal, D. Atlanto-axial is ellipsoid joint
B: Atlanto-occipital joint has flexion and extension movement
Answer: B: Atlanto-occipital joint has flexion and extension movement 
Explanation: None