Question

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sleep in which heart rate, breathing, and brain activity are steady

irregular or rapid - eye - movement sleep
regular or nonrem sleep
visual acuity
waking activity
alert inactivity

Explanation:

Non - REM sleep is characterized by steady heart rate, breathing, and brain activity. In contrast, REM sleep has more variable physiological responses. Visual acuity relates to vision, waking activity is when a person is awake, and alert inactivity is not related to this sleep - state description.

Answer:

regular or nonREM sleep