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 tooth has a non functional cusp 
Select and explain. 
A. Lower 1st premolar, B. Upper 1st premolar, C. Lower 2nd premolar, D. Upper 1st premolar
A: Lower 1st premolar
Answer: A: Lower 1st premolar 
Explanation: None