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
The earliest manifestation of cell injury is: 
Select and explain. 
A. Vasoconstriction, B. Increased vascular permeability, C. Phagocytosis, D. Apoptosis
A: Vasoconstriction
Answer: A: Vasoconstriction 
Explanation: Vasodilation is one of the earliest manifestations of acute inflammation; sometimes it follows a transient constriction of aerioles, lasting a few seconds. Vasodilation first involves the aerioles and then leads to opening of new capillary beds in the area. The result is increased blood flow, which is the cause of heat and redness (erythema) at the site of inflammation. Vasodilation is induced by the action of several mediators, notably histamine and nitric oxide (NO), on vascular smooth muscle. Ref: Robbins 8th edition, Chapter 2