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
Which of the following is a smallest posterior tooth: 
Select and explain. 
A. Maxillary first premolar, B. Mandibular first premolar, C. Maxillary second premolar, D. Mandibular second premolar
B: Mandibular first premolar
Answer: B: Mandibular first premolar 
Explanation: None