Which of the following is a sign of hypoxia?

The correct answer is drowsiness, as it is a clear indicator of hypoxia, which is a condition characterized by insufficient oxygen reaching the tissues. When the body is deprived of adequate oxygen, the brain is particularly affected, leading to symptoms such as fatigue, confusion, and drowsiness. This reduced mental alertness is a direct consequence of brain cells not receiving enough oxygen to function optimally.

In contrast, the other choices—such as increased reaction time, enhanced judgment, and improved coordination—are generally associated with normal or enhanced cognitive and physical functioning. Hypoxia impairs these abilities, resulting in slower reaction times and diminished judgment and coordination. Thus, drowsiness stands out as a direct sign of oxygen deficiency in the body's systems.