What term describes the fluctuation in body temperature that occurs within a 24-hour period?

Explanation

The correct answer is B, 'Circadian rhythm,' which refers to the natural, internal process that regulates the sleep-wake cycle and repeats roughly every 24 hours, including changes in body temperature. Acclimation and acclimatization relate to long-term physiological adjustments to environmental changes, while heat loss refers to the process of losing heat, not the cyclical temperature variation.