This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ecotopic Pregnancy, Subject name: Gynaecology & Obstetrics
[{'content': 'Most valuable diagnostic test in case of suspected ectopic pregnancy: \nSelect and explain. \nA. Serial b-hCG revels, B. Transvaginal USG, C. Progesterone measurement, D. Culdocentesis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. is b, i.e. Transvaginal USGRef. Dutta Obs. 7/e, p 182, 183; Williams Gynae 1/e, p 162, 163; Novak 14/e, p 611; Williams Obs. 22/e, p 259, 23/e, p 242, 43"As explained earlier transvaginal ultrasound is the best available diagnostic modality for diagnosing ectopic pregnancy. Vaginal sonography yields correct pre-operative diagnosis of ectopic pergnancy in 91% cases. It decreases the need for diagnostic laparoscopy or curettage or both to establish the diagnosis of ectopic pregnancy" --Williams Gynae 1/e, p 163"Vaginal sonography has become the imaging method of choice." --Williams Obs. 22/e, p 259', 'role': 'assistant'}]