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
Branchial fistula is persistent of: 
Select and explain. 
A. 1st branchial cleft., B. 1st branchial arch., C. 2nd branchial cleft., D. 2nd branchial arch.
C: 2nd branchial cleft.
Answer: C: 2nd branchial cleft. 
Explanation: None