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: Gynaecology & Obstetrics
[{'content': 'Miladevi is a diagnosed case of ectopic gestation, which of the following will be the most reliable indicator: \nSelect and explain. \nA. Arias stella reaction, B. Culdocentesis showing blood in the posterior cul-de-sac, C. Absence of the normal doubling of HCG levels, D. No gestational sac in USG', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]