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: Surgery
[{'content': 'Which of the following is more aggressive rectal carcinoma - \nSelect and explain. \nA. Adenocarcinoma, B. Secondary mucoid carcinoma, C. Signet ring carcinoma, D. Squamous cell carcinoma', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]