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': 'When preparing a 3/4th crown on maxillary incisor tooth, the proximal grooves should generally be parallel to the \nSelect and explain. \nA. Long axis of the tooth, B. Gingival 2/3rd of the labial surface, C. Incisal 2/3rd of the labial surface, D. Short axis of the tooth', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]