This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Rectum and anal canal, Subject name: Surgery
All are true regarding rectal carcinoma EXCEPT: 
Select and explain. 
A. Early morning spurious diarrhea and tenesmus can occur, B. Adenocarcinoma is a rare variant of rectal carcinoma., C. Growth confined to the rectal mucosa is stage A of modified Duke's staging., D. Hamann's operation is done in old debilitated patients.
B: Adenocarcinoma is a rare variant of rectal carcinoma.
Answer: B: Adenocarcinoma is a rare variant of rectal carcinoma. 
Explanation: Rectal carcinoma: MC site of large bowel malignancy Adenocarcinoma is the most common variant of rectal carcinoma. C/F- MC symptom- bleeding PR Early morning spurious diarrhea Tenesmus Weight loss IOC- rigid sigmoidoscopy+ biopsy Hamann's operation is done in old debilitated patients.