**Core Concept:** Non-Rapid Eye Movement (NREM) sleep is a stage of the sleep cycle that includes three stages: N1, N2, and N3. These stages are important for maintaining overall health, cognitive function, and memory consolidation.

**Why the Correct Answer is Right:** NREM sleep is a crucial part of the sleep cycle, which also includes Rapid Eye Movement (REM) sleep. The correct answer, **"NREM Sleep is a stage of sleep cycle"**, highlights the significance of NREM sleep and its role in the sleep cycle. NREM sleep contributes to the overall health, cognitive function, and memory consolidation of an individual.

**Why Each Wrong Option is Incorrect:**

A. "Rapid Eye Movement (REM) Sleep is True": This option is incorrect because it contradicts the correct answer, as REM sleep is the other stage of the sleep cycle, not NREM sleep.

B. "Sleep is True": This option is incorrect because it is too broad and does not specifically address the nature of NREM sleep.

C. "Sleep Deprivation is True": This option is incorrect because it focuses on the consequence of sleep deprivation rather than explaining NREM sleep itself.

D. "Sleep is Necessary": This option is incorrect because it is too broad and does not specifically address the nature of NREM sleep.

**Clinical Pearl / High-Yield Fact:** Understanding and maintaining an appropriate balance of both NREM and REM sleep is vital for optimal health and cognitive function. Insufficient or excessive sleep can lead to various health issues, such as fatigue, cognitive decline, and sleep disorders.

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**Correct Answer:** NREM Sleep is a stage of sleep cycle.