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': 'Prognosis of malignant melanoma depends on ? \nSelect and explain. \nA. Grade of tumor, B. Spread of tumor, C. Depth of invasion, D. Metastasis', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Depth of invasion", 'role': 'assistant'}]