This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Nightmare is seen in : 
Select and explain. 
A. REM sleep, B. Stage II NREM sleep, C. Stage IV NREM sleep, D. Stage I NREM sleep
A: REM sleep
Answer: A: REM sleep 
Explanation: A i.e. REM sleep