When Making Rounds on the Night Shift, the Nurse Observes

When making rounds on the night shift, the nurse observes her client to be in a deep sleep. His muscles are very relaxed. When he arouses as the nurse changes the intravenous (IV) tubing, he is confused. What stage of sleep was the client most likely experiencing?

A) NREM I
B) NREM II
C) NREM III
D) REM