Why is a major vein severed in the neck particularly dangerous?

A major vein severed in the neck is particularly dangerous because if the injury is significant, it can lead to a condition known as air embolism. In this scenario, the negative pressure created by the severed vein can draw air into the bloodstream. When air bubbles enter the circulatory system, they can travel to the heart, lungs, and other vital organs, potentially causing life-threatening complications such as cardiac arrest or respiratory distress.

This situation is exacerbated in the neck area, where major veins, like the jugular vein, are located close to the surface and are highly susceptible to injury. The rapid loss of blood from the vein can also lead to hypovolemic shock, which further complicates the victim's condition. The other options, while concerning, do not capture the immediate and severe risk associated with the introduction of air into the bloodstream due to a major vein being compromised.