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: Unknown
Most common site for small intestinal carcinoma is? 
Select and explain. 
A. Duodenum, B. Jejunum, C. Ileum, D. All are affected equally
A: Duodenum
Answer: A: Duodenum 
Explanation: Ans is 'a' i.e. duodenum "Adenocarcinoma is the most frequent carcinoma found in the small intestine. The upper small intestine is the most common site for carcinoma with duodenum, jejunum, and ileum involved in 40%, 38% % 20% respectively". - Cancer Metastasis, Molecular and Cellular Mechanisms and Clinical Intervention.