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.

• A. I & II.
• B. II & III.
• C. I & III.
• D. I, II, & III

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the concept of the sleep cycle. The sleep cycle is not a 24-hour cycle; it refers to the stages of sleep that repeat several times during a night's sleep.
2. Step 2: Evaluate statement I. The sleep cycle does not refer to the 24-hour cycle of sleeping and waking. This is a description of the circadian rhythm, not the sleep cycle.
3. Step 3: Evaluate statement II. On average, people do go through 4-6 sleep cycles per night, each lasting about 90 minutes.
4. Step 4: Evaluate statement III. The sleep cycle has two general phases: Non-REM (NREM) and REM (Rapid Eye Movement) sleep.
5. Step 5: Determine which statements are true based on the evaluations. Statements II and III are true, while statement I is false.