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: Surgery
Structures not removed in radical neck dissectiona) X nerveb) X1 nervec) Tail of parotidd) Parotid and post-auricular nerve 
Select and explain. 
A. acd, B. bc, C. bd, D. ac
A: acd
Answer: A: acd 
Explanation: None