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
Eruption of the permanent maxillary second molar prior to the maxillary second premolar is: 
Select and explain. 
A. Normal and desirable, B. Abnormal and undesirable, C. Abnormal and desirable, D. Normal and undesirable
B: Abnormal and undesirable
Answer: B: Abnormal and undesirable 
Explanation: None