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: Anatomy
[{'content': 'Structures descending through foramen magnum are all except: \nSelect and explain. \nA. Lower part of medulla., B. Tonsils of cerebellum., C. Membrana tectoria., D. Anterior and posterior spinal arteries.', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]