What is a common symptom of hypoxia?

Drowsiness is a common symptom of hypoxia because the brain is highly sensitive to oxygen levels. When the body does not receive adequate oxygen, neurological functions can become impaired. The central nervous system, which includes the brain, relies on oxygen to produce energy and maintain alertness. A deficiency can lead to reduced cognitive function, resulting in drowsiness or lethargy as the brain's activity is decreased.

The other choices, while they may be related to various health conditions, are not as directly associated with hypoxia. Nausea can occur with various other ailments, severe headaches can be symptomatic of numerous issues including dehydration or tension, and high blood pressure is typically not a direct result of low oxygen levels and may be influenced by other factors, such as stress or cardiovascular health. Thus, drowsiness stands out as a particularly clear indicator of hypoxia due to the direct impact on brain function.