Which of the following illustrates behavioral thermoregulation?

Behavioral thermoregulation refers to the strategies that animals use to control their body temperature in response to environmental conditions. Seeking shade or water in hot conditions is a clear example of this, as it involves actively changing one's environment to manage thermal stress. By moving to a cooler area or finding water, an animal reduces its body temperature and prevents overheating, effectively regulating its internal environment through behavior rather than physiological changes.

In contrast, the other options primarily involve physiological responses or are mechanisms that occur in reaction to temperature changes rather than strategies to seek out a more favorable environment. Shivering in cold temperatures is a physiological response to generate warmth, while increased heart rate is often a part of the body's response to stress or temperature extremes, but neither involves actively seeking changes in the external environment. Similarly, metabolic adjustments represent internal changes the body makes to regulate temperature but do not reflect behaviors aimed specifically at temperature control.