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 lower 2nd molar occur before lower 2nd premolar; probable reason being 
Select and explain. 
A. Crowding, B. Impaction of lower 2nd premolar, C. Premature exfoliation of primary 2nd molar, D. None of the above
B: Impaction of lower 2nd premolar
Answer: B: Impaction of lower 2nd premolar 
Explanation: None