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
Shape of class 1 preparation of lower first premolar : 
Select and explain. 
A. Dumbell shape, B. Y shape, C. Butterfly shape, D. No definite shape
C: Butterfly shape
Answer: C: Butterfly shape 
Explanation: Shapes of class I preparation: