This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abdomen & Pelvis, Subject name: Anatomy
Choose the appropriate lettered structure in this CT scan of the abdomen at the level of the upper lumbar vertebra. Which structure is a direct branch of the aorta and supplies blood to the ascending and transverse colons? 
Select and explain. 
A. A, B. B, C. C, D. D
D: D
Answer: D: D 
Explanation: (d) The superior mesenteric artery, a direct branch of the aorta, supplies blood to the ascending and transverse colons.