You Are Monitoring the Sleep of a Healthy Young Woman

You are monitoring the sleep of a healthy young woman. You note that a high percentage of her sleep has been occupied by REM sleep for the last hour. Which of the following is probably true?

A) She has been having difficulty falling asleep.
B) You are recording during the first hour or two of the night.
C) You are recording during the middle of the night.
D) You are recording near the end of her night's sleep.