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
Slow wave sleep associated with: 
Select and explain. 
A. Dreams, B. Cardiac arrhythmia, C. Penile intumescence, D. Delta activity
D: Delta activity
Answer: D: Delta activity 
Explanation: D i.e. Delta activity