Which of the following statements are true about the sleep cycle.
I. The sleep cycle refers to the 24-hour cycle of sleeping and waking.
II. On average, people go through 4-6 cycles per night.
III. The sleep cycle has two general phases.
Derrick brings his car to a sudden halt as he notices that the light has already turned red.
Luciana wobbles just a bit as she tries to walk after drinking three glasses of wine.
Orlando carefully calculates his taxes two weeks before taxes are due.
Helena fights to keep her eyes open as she reads a bedtime story to her children.