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 of the following is main cause of pain during pulpal injury progression? 
Select and explain. 
A. Increased vascular permeability, B. Decreased threshold of nerve fibres to pain, C. Arteriolar dilatation, D. Decrease pressure
A: Increased vascular permeability
Answer: A: Increased vascular permeability 
Explanation: None