What is Elka most likely experiencing?
A sleep researcher is recording details of Elka’s sleep patterns in a sleep laboratory. Elka’s EEG recording shows that she is currently experiencing lowfrequency, high-amplitude delta waves. Her EOG shows no sign of activity. The researcher can hear Elka talking, but cannot make out what she is saying.
A. REM sleep. B. Muscle paralysis. C. NREM stage 2 sleep. D. Stage 4 sleep.