This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Psychiatric Illness, Subject name: Pharmacology
A 32 - year- old male psychiatric patient complains that he feels tremors on movement. He is on some medication and feels always thirsty and frequently has to urinate. The most likely drug he is taking is? 
Select and explain. 
A. Valproic acid, B. Clozapine, C. Lithium, D. Risperidone
C: Lithium
Answer: C: Lithium 
Explanation: Tremors and symptoms of nephrogenic diabetes insipidus are due to side effects of lithium administration that can occur at blood levels within therapeutic range. Clozapine is associated with sedation and agranulocytosis