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: Pharmacology
Which of the following drugs is both effective and safe to use in a pregnant patient suffering from bipolar disorder ? 
Select and explain. 
A. Carbamazepine, B. Lithium, C. Olanzapine, D. Valproic acid
C: Olanzapine
Answer: C: Olanzapine 
Explanation: None