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
Lower primary 1st molar has 
Select and explain. 
A. 3 pulp horns and 3 root canals, B. 4 pulp horns and 3 root canals, C. 4 pulp horns and 4 root canals, D. 3 pulp horns and 4 root canals
B: 4 pulp horns and 3 root canals
Answer: B: 4 pulp horns and 3 root canals 
Explanation: None