Read the passage about prebiotics and sleep carefully and then answer the question: Prebiotics are the lesser-known gut-health promoters which serve as food for good bacteria inside the gut. "We found that dietary prebiotics can improve non-REM (random eye movement) sleep, as well as REM sleep after a stressful event," said Robert Thompson, a PhD researcher at University of Colorado Boulder in the U.S. Prebiotics are dietary fibres found naturally in foods like artichokes, raw garlic, leeks and onions. When beneficial bacteria digest prebiotic fibre, they not only multiply, improving overall gut health, but they also release metabolic by-products. Researchers fed three-week-old male rats a diet of either standard chow or chow that included prebiotics. They then monitored the rats body temperature, gut bacteria and sleep-wake cycles using electroencephalogram (EEG), or brain activity testing over time. Findings revealed that the rats on the prebiotic diet spent more time in non-rapid-eye-movement (NREM) sleep, which is restful and restorative, than those on the non-prebiotic diet. What type of sleep is described as restful and restorative?

Introduction / Context:
This reading comprehension item focuses on identifying a specific detail in the passage about sleep and prebiotics. The passage contrasts two types of sleep, non-rapid-eye-movement (NREM) sleep and rapid-eye-movement (REM) sleep, and explains an experiment conducted on rats. The question asks which type of sleep is described as “restful and restorative”.

Given Data / Assumptions:
- The passage states that rats on a prebiotic diet spent more time in non-rapid-eye-movement (NREM) sleep. - It adds that this type of sleep is “restful and restorative”. - REM sleep is mentioned as another sleep phase but is not described with those same words. - EEG is the monitoring technique, and ECG is not even mentioned in the original text.

Concept / Approach:
This is a straightforward factual detail question. The correct approach is to locate the sentence in which the phrase “restful and restorative” appears and read which term it directly qualifies. While general knowledge may suggest that both NREM and REM play roles in health, the exam expects an answer based strictly on the wording of the passage. Careful attention to the exact phrase allows the candidate to identify the correct type of sleep without confusion.

Step-by-Step Solution:
Step 1: Re-read the part of the passage that describes the findings of the experiment. Step 2: Identify the key sentence: “Findings revealed that the rats on the prebiotic diet spent more time in non-rapid-eye-movement (NREM) sleep, which is restful and restorative, than those on the non-prebiotic diet.” Step 3: Note that the relative clause “which is restful and restorative” directly follows “non-rapid-eye-movement (NREM) sleep”. This indicates that the description refers to NREM sleep. Step 4: Confirm that REM sleep is mentioned but not given this particular description in the quoted sentence. Step 5: Check that EEG and ECG are not types of sleep but rather medical tests; daytime naps are not discussed in the passage at all. Step 6: Conclude that NREM is the correct answer.

Verification / Alternative check:
To verify, substitute each option into the phrase from the passage. Only “NREM” fits logically and grammatically into “NREM sleep, which is restful and restorative”. Substituting REM or EEG would mismatch the original wording. The passage clearly differentiates between the research technique (EEG), the sleep phases (NREM and REM), and the outcome measures. This direct textual evidence confirms NREM as the correct choice.

Why Other Options Are Wrong:
REM: The passage mentions REM sleep but does not describe it as “restful and restorative” in the key sentence. EEG: This is an electroencephalogram, a brain activity test used to monitor sleep-wake cycles, not a type of sleep. ECG: This is a heart monitoring test (electrocardiogram) and is not even part of the passage. Daytime naps: The passage does not refer to naps; it focuses on sleep stages in laboratory rats.

Common Pitfalls:
A frequent error is relying on real-world knowledge instead of the passage itself. Some students may think of REM as important for dreaming and mental restoration and thus may be tempted to choose it. However, the exam expects answers based on explicit information in the text. Another pitfall is confusing technical terms such as NREM, REM, and EEG. Reading slowly and linking each term to its function as described in the passage prevents such confusion.

Final Answer:
The type of sleep described in the passage as “restful and restorative” is NREM sleep.