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: Pathology
A 5 years old boy punctures his thumb with a rusty nail. Four hours later, the thumb appears red and swollen. Initial swelling of boy's thumb is primarily due to which of the following mechanism? 
Select and explain. 
A. Decreased intravascular hydrostatic pressure, B. Decreased intravascular oncotic pressure, C. Increase capillary permeability, D. Increase intravascular oncotic pressure
C: Increase capillary permeability
Answer: C: Increase capillary permeability 
Explanation: The vascular reactions of acute inflammation consist of changes in the flow of blood and the permeability of vessels, both designed to maximize the movement of plasma proteins and leukocytes out of the circulation and into the site of infection or injury.