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: Psychiatry
Test to differentiate between psychological and organic erectile dysfunction: NEET 13 
Select and explain. 
A. Pharmacologically induced penile erection therapy, B. Nocturnal penile tumescence, C. Sildenafil induced erection, D. Squeeze technique
B: Nocturnal penile tumescence
Answer: B: Nocturnal penile tumescence 
Explanation: Ans. Nocturnal penile tumescence