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
Swelling situated in the posterior triangle of the neck 
Select and explain. 
A. Cystic hygroma., B. Branchiogenic carcinoma., C. Collar stud abscess., D. All of the above.
A: Cystic hygroma.
Answer: A: Cystic hygroma. 
Explanation: None