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
Pulp responds to all stimuli by pain because it has only 
Select and explain. 
A. Free nerve endings, B. Krause end bulbs, C. Pacinian corpuscle, D. Ruffini corpuscle
A: Free nerve endings
Answer: A: Free nerve endings 
Explanation: None