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
A person laughs to a joke, then suddenly loses tone of all muscles. Diagnosis is: DNB 09; JIPMER 13 
Select and explain. 
A. Cataplexy, B. Catalepsy, C. Sleep attack, D. Sleep paralysis
A: Cataplexy
Answer: A: Cataplexy 
Explanation: Ans. Cataplexy