Task: Class Definition Understanding (ontology: Human_Society/EmotionOntology)

Which of the following definitions best describes 'circadian sleep/wake cycle, sleep'?

A. A stage in the circadian sleep cycle during which dreams occur and the body undergoes marked changes including rapid eye movement, loss of reflexes, and increased pulse rate and brain activity.
B. The part of the circadian sleep/wake cycle where the organism is not asleep.
C. "Behavior related to all sleep stages in the circadian sleep/wake cycle other than REM sleep." [NBO:GVG]
D. The part of the circadian sleep/wake cycle where the organism is asleep.

Answer: The part of the circadian sleep/wake cycle where the organism is asleep.