From which stage of sleep is it most difficult to be awakened?

Name: From which stage of sleep is it most difficult to be awakened?
Brand: Quizplus
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Question

Quizplus · Accepted Answer

Stage IV, also known as delta sleep, is the deepest stage of non-rapid eye movement (NREM) sleep. It is during this stage that the body experiences the most physiological changes, such as a slowing of breathing, heart rate, and brain activity. Waking up from this stage can be difficult and individuals are often disoriented and groggy if they are awakened suddenly.

From Which Stage of Sleep Is It Most Difficult to Be