This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anti-Cancer, Subject name: Pharmacology
[{'content': 'Doc for Her 2 positive breast carcinoma is: \nSelect and explain. \nA. Trastuzumab, B. Tamoxifen, C. Exemestane, D. Fluvestrant', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. a. TrastuzumabRef: Goodman Gilman 13th E/P1209Her-2 PositiveDrug of Choice for Breast Cancer ER positiveDrug of choice: TrastuzumabDrug of choice in Trastuzumab resistance: LapatinibPremenopausal PostmenopausalDrug of Choice: Tamoxifen Drug of Choice: Aromatase Inhibitors likeExemestane', 'role': 'assistant'}]