Delta waves are the slowest waves and occur during periods of deep sleep. It is also known as slow wave sleep. The answer would not be REM sleep, because it is characterized by saw-tooth waves. Sleep onset stage may be characterized by alpha (i.e. drowsy) and theta (i.e. light sleep) waves. Stage two of sleep typically shows k-complexes and sleep spindles, which are not seen with delta waves. 

REM (rapid eye-movement) sleep is the fifth and final stage of sleep during which the body is in it's deepest sleep. Dreaming is most frequent, most vivid, and most memorable during REM sleep; however, other dreaming can occur during the other sleep stages. 

The circadian rhythm is the 24-hour biological cycles found in humans and other species. Circadian rhythms are influential in regulating sleep, blood pressure, urine production, hormonal secretions, and other physical functions. Although each of these could be affected, the most comprehensive answer is circadian rhythm. 

Over the course of the four repetitions, REM sleep starts as a fairly brief period of about 45 minutes. By the end of the fourth repetition, the REM period of the sleep cycle is substantially longer. Dreaming is most associated with REM sleep, and dreaming during REM stays the same over the course of the sleep cycle. 

Sleep deprivation and partial sleep deprivation have many negative consequences on our physical and mental well-being. Studies have shown that people who consistently sleep less than 7 hours are at increased risk for overall mortality. 

Sleep can be divided into REM and NREM sleep. Stages 1 to 4 are characterized by non-rapid eye movement (i.e. NREM) sleep. Stage 5 is characterized by rapid eye movement (i.e. REM). Beta waves occur during normal wakefulness and are not associated with sleep. As the body begins to fall asleep and enters stage 1, alpha waves become present. During stage 2 theta waves and sleep spindles emerge. During stages 3 and 4, delta waves are present.

"Stage 4" has the slowest brain waves. This is because it's the deepest stage of sleep. The brain, if awoken in this stage, would take a long time to be able to perform certain actions because those brain waves have to be "sped up" to be able to engage in conscious action. 

"Night terrors usually have a story or plot to them" is the correct answer. This is the only answer that is not true. Nightmares usually have a story or a plot to them, not night terrors. 

During rapid eye movement (REM) sleep, the random movement of the eyes is not voluntary because the person is soundly sleeping. REM sleep is essential for humans to feel well-rested and thrive during waking hours.

Wanda probably has insomnia. Insomnia refers to chronic problems in getting adequate sleep stemming from difficulty falling asleep, staying asleep, or persistently waking up early. Hypersomnia is the opposite of insomnia when someone gets too much sleep. Sleep apnea is a condition when respiration is periodically stopped during sleep. Narcolepsy is a sleep disorder characterized by sudden irresistible feelings of sleepiness during normal waking periods.