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
Which of the following is a retroperitoneal structure: 
Select and explain. 
A. Caecum, B. Transverse colon, C. Descending colon, D. Sigmoid colon
C: Descending colon
Answer: C: Descending colon 
Explanation: Descending colon