Adam slept peacefully through most of the night and then at 5:00 a.m. he woke up sobbing. When his parents asked what had scared him, he told them that monsters came through the wall to attack him, and no matter how fast he ran he couldn't get away. Even though his parents told him it was just a bad dream, Adam was afraid to go back to sleep. From this description, what did Adam experience? 

A)  a nightmare 
B)  a night terror 
C)  sleep seizure 
D)  sleep apnea