This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Pharmacology
[{'content': 'The drug of choice for treatment of thyrotoxicosis during pregnancy is \nSelect and explain. \nA. Iodine therapy, B. Carbimazole, C. Propylthiouracil, D. Methimazole', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Refer KDT 6 /e p 250 Propylthiouracil does not cross placenta and us therefore The drug of choice in first trimester pregnancy', 'role': 'assistant'}]