Robert Has Been Feeling Very Tired the Last Few Weeks

Robert has been feeling very tired the last few weeks and tells his doctor that he only sleeps two hours a night. Before making a diagnosis, his doctor asks Robert to spend a night in the sleep lab connected to an EEG. Several times that night, Robert's brain waves have a low frequency and high amplitude. This indicates to the doctor that Robert is

A) only experiencing the early stages of light sleep
B) waking several times during the night
C) experiencing several cycles through the deep stages of sleep
D) spending an unusual amount of time in REM sleep