Which of the following can increase pulse rate?

The correct choice regarding factors that can increase pulse rate is indeed that extreme temperature change is a significant influence. When the body is exposed to extreme conditions—whether heat or cold—its response is to adjust various physiological mechanisms to maintain homeostasis. In a hot environment, for example, the heart rate typically increases to help facilitate heat dissipation through increased blood flow to the skin. Similarly, in cold conditions, the body may also elevate the heart rate to ensure adequate circulation and retain core temperature.

Fasting can affect the body in various ways, but it does not consistently lead to an increase in pulse rate. Instead, fasting can lead to a decrease in metabolic activity, which may result in a slower pulse rate in many cases as the body conserves energy. Dehydration can potentially affect heart rate by causing an increase in heart rate due to decreased blood volume and compensatory mechanisms. However, under certain conditions, it might lead to a decreased rate due to the body's overall state.

Therefore, while extreme temperature changes are a well-known factor leading to an increased pulse rate, both fasting and dehydration do not clearly or consistently increase pulse rate across all scenarios, which makes the response linked to extreme temperature change more direct and apparent.