This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gynaecological oncology, Subject name: Gynaecology & Obstetrics
[{'content': 'Tamoxifen predisposes to : \nSelect and explain. \nA. Endometrial cancer, B. Ovarian cancer, C. Cervical cancer, D. Vaginal cancer', 'role': 'user'}, {'content': "Answer: A \nExplanation: In Breast Cancer although tamoxifen improves the survival period, it causes endometrial hyperplasia and cancer, and requires regular monitoring with ultrasound study of endometrium and endometrial biopsy. Reference: Shaw's Textbook of Gynaecology 16th edition page no 540", 'role': 'assistant'}]