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
DOC for rapid cycling MDP 
Select and explain. 
A. Li, B. Valproate, C. Calcium Channel Blocker, D. All
B: Valproate
Answer: B: Valproate 
Explanation: B i.e. Valproate