About 3 hours after he falls asleep,Bobby often sits up in bed screaming incoherently.His mother tries to awaken him,but with no success.The next morning,he remembers nothing.It appears that Bobby suffers from

A) night terrors.
B) narcolepsy.
C) sleep spindles.
D) sleep apnea.

Bobby's symptoms are consistent with night terrors, which are characterized by the sudden awakening from deep sleep with screams, sweating, and a racing heart. Unlike nightmares, people with night terrors usually don't remember the episode the next morning. Narcolepsy involves excessive daytime sleepiness and sudden episodes of sleep, sleep spindles are brief bursts of brain activity during sleep, and sleep apnea is characterized by pauses in breathing during sleep.