Final answer:
Based on the symptoms and the information about Wally's sleep stage just before waking up, the most appropriate description is that Wally had just experienced a nightmare. the correct option is (c).
Step-by-step explanation:
In the scenario described, Wally awoke screaming, shaking, and sweating with a rapid heartbeat. The parents, Ward and June, hooked Wally up to an electroencephalogram (EEG) and noted that Wally was in stage 4 sleep just before he awoke. The key characteristic here is that Wally experienced a nightmare.
Options:
a) Sleepwalking: Sleepwalking involves performing activities that are normally associated with wakefulness while in a state of sleep. It does not typically involve awakening with screaming, shaking, and sweating.
b) Sleep apnea: Sleep apnea is a condition characterized by pauses in breathing during sleep, leading to disrupted sleep patterns. It is not directly associated with waking up from a nightmare.
c) Nightmare: A nightmare is a vivid, frightening dream that can cause a person to wake up with strong emotions such as fear or anxiety. This option is correct based on the scenario provided.
d) Sleep paralysis: Sleep paralysis is a temporary inability to move or speak that occurs when falling asleep or waking up. It is not directly related to the description of waking up from a nightmare.
Based on the symptoms and the information about Wally's sleep stage just before waking up, the most appropriate description is that Wally had just experienced a nightmare.