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
Structure not enclosed by carotid sheath - 
Select and explain. 
A. Internal carotid artery, B. Vagus, C. Cervical sympathetic chain, D. Internal jugular vein
C: Cervical sympathetic chain
Answer: C: Cervical sympathetic chain 
Explanation: Carotid sheath contains ICA, IJV and vagus nerve. In upper part of sheath there are IX, XI, XII nerves also.