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: Pathology
[{'content': "In Duke's classification of cancer rectum, B2 denotes - \nSelect and explain. \nA. Growth extends to perirectal fat, B. Regional nodes involved, C. Limited to thickness of bowel wall, D. Hepatic metastasis", 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]