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
According to Mount and Hume classification, an enlarged carious lesion in contact area region will be denoted as: 
Select and explain. 
A. 1.3, B. 2.3, C. 3.2, D. 2.2
B: 2.3
Answer: B: 2.3 
Explanation: MOUNT AND HUME CLASSIFICATION