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
Preveebral space thickness in adult at C6-C7 level is 
Select and explain. 
A. 7mm, B. 15mm, C. 22mm, D. 30mm
C: 22mm
Answer: C: 22mm 
Explanation: 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