This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Large intestine, Subject name: Surgery
[{'content': 'According to Modified Astler-Collar Classification for colorectal cancer, lymph node invasion with penetration of the entire bowel wall is included in stage: \nSelect and explain. \nA. B1, B. B2, C. C1, D. C2', 'role': 'user'}, {'content': "Answer: D \nExplanation: Modified Duke's (Modified Astler-Collar) classification Stage Description A Confined to the mucosa B1 Paially penetrated the muscularis propria B2 Fully penetrated the muscularis propria C1 Lymph node invasion without penetration of the entire bowel wall C2 Lymph node invasion with penetration of the entire bowel wall D Distant metastatic disease", 'role': 'assistant'}]