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: Dental
[{'content': 'The main form of iron carbide found in 18-8 steel: \nSelect and explain. \nA. Martensite, B. Ferrite, C. Austenite, D. Pearlite', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]