This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Skeletal system, Subject name: Radiology
[{'content': 'Preveebral space thickness in adult at C6-C7 level is \nSelect and explain. \nA. 7mm, B. 15mm, C. 22mm, D. 30mm', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Upper limits of preveebral space thickness varies with the cervical veebral level in an adult as follows : At C1 level : 10 mm At C2 level : 5 mm At C3 level : 7 mm At C5 level : 22 mm At C6-C7 level : 22 mm', 'role': 'assistant'}]