The correct answer is C. Conrad exhibits more time spent in REM sleep.
When individuals are routinely awakened during REM sleep, as in Conrad's case during the previous sessions, they tend to accumulate REM sleep when they are finally allowed to sleep undisturbed. This phenomenon is known as REM rebound. Consequently, during session 19, it is expected that Conrad will spend more time in REM sleep compared to if he had not been deprived of it.