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
A characteristic feature of lingual surface of the mandibular first premolar is: 
Select and explain. 
A. Rudimentary lingual cusp, B. Mesial marginal ridge, C. Mesiolingual developmental groove, D. Lingual triangular ridge
C: Mesiolingual developmental groove
Answer: C: Mesiolingual developmental groove 
Explanation: A characteristic of the lingual surface of the mandibular first premolar is the mesiolingual developmental groove. This groove acts as a line of demarcation between the mesiobuccal lobe and the lingual lobe and extends into the mesial fossa of the occlusal surface.