What characterizes the different stages of sleep?

The correct choice highlights that the different stages of sleep are characterized by distinct patterns of brain waves, which can be measured using an electroencephalogram (EEG). During sleep, the brain exhibits various wave patterns, identified as delta waves during deep sleep, theta waves during light sleep, and alpha waves when transitioning into sleep. These brain wave patterns correspond to the different stages within the sleep cycle, which include light sleep, deep sleep, and REM (Rapid Eye Movement) sleep.

While changes in body temperature, hormone production, and blood pressure do occur during sleep, they are not as defining for the classification of sleep stages as the brain wave patterns. For instance, body temperature tends to decrease during sleep, and certain hormones such as melatonin are produced in greater amounts during sleep, but these changes don't provide specific information about which sleep stage a person is in. Thus, understanding the various brain wave patterns is fundamental to recognizing and characterizing the different stages of sleep effectively.