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
The interincisal angle between deciduous incisors is: 
Select and explain. 
A. 100 degrees, B. 120 degrees, C. 150 degrees, D. 170 degrees
C: 150 degrees
Answer: C: 150 degrees 
Explanation: 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 dentition. This increases the arch perimeter.
 
Ref: Textbook of orthodontics Gurkeerat Singh 2nd ed pg no 46