Which of the following is a symptom of hyperthermia?

Hyperthermia occurs when the body temperature rises significantly above normal levels, often due to prolonged exposure to heat or strenuous activity in hot environments. One of the body's responses to this condition is the onset of nausea. Nausea can be attributed to multiple factors during hyperthermia, including the body's struggle to maintain homeostasis and the effects of dehydration that often accompany excessive heat exposure. As the body overheats, physiological processes become disrupted, resulting in feelings of sickness or discomfort in the stomach.

In contrast, the other symptoms mentioned do not directly correlate with hyperthermia. Cold extremities typically suggest a drop in body temperature (hypothermia) or poor circulation, shallow breathing does not specifically indicate hyperthermia and may relate more to anxiety or respiratory issues, and hiccups are usually not a direct symptom of hyperthermia but can occur due to irritation of the diaphragm or nerves, which is not linked to overheating. Thus, nausea stands out as the symptom most closely associated with hyperthermia.