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
Access cavity shape in mandibular 1st molar with 4 canals 
Select and explain. 
A. Trapezoidal, B. Round, C. Oval, D. Triangular
A: Trapezoidal
Answer: A: Trapezoidal 
Explanation: None