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 interincisal angle between deciduous incisors is: \nSelect and explain. \nA. 100 degrees, B. 120 degrees, C. 150 degrees, D. 170 degrees', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Primary teeth are upright, but permanent teeth incline to the labial surface, thus decreasing the inter-incisal angle from about 150 degrees in the deciduous dentition to 123 degrees in the permanent\xa0dentition. This increases the arch perimeter.\n\xa0\nRef: Textbook of orthodontics Gurkeerat Singh 2nd ed pg no 46', 'role': 'assistant'}]