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 of mandibular 1st molar is: 
Select and explain. 
A. Oval, B. Rounded triangle, C. Rhomboid, D. None of the above
B: Rounded triangle
Answer: B: Rounded triangle 
Explanation: 1st choice for access cavity preparation in mandibular 1st molar is trapezoidal.
2nd choice is rounded triangle.