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
Basanti, a 28yrs aged female with a history of 6 weeks of amenorrhea presents with pain in abdomen; USG shows fluid in pouch of douglas. Aspiration yields dark colour blood that fails to clot. Most probable diagnosis is: 
Select and explain. 
A. Ruptured ovarian cyst, B. Ruptured ectopic pregnancy, C. Red degeneration of fibroid, D. Pelvic abscess
B: Ruptured ectopic pregnancy
Answer: B: Ruptured ectopic pregnancy 
Explanation: Aspiration of blood clots or dark coloured blood that fails to clot, signifies collection of intraperitonial blood. Pain in abdomen and blood in pouch of doglas in a woman of child bearing age (28yrs) with history of 6 weeks amenorrhea suggests a diagnosis of ruptured ectopic pregnancy. Ref: Ultrasound in Obstetrics and Gynecology, Volume 1 By Eberhard Merz, F. Bahlmann, 2004, Page 73 ; Management of Common Problems in Obstetrics and Gynecology Edited By T. Murphy Goodwin, Main N. Montoro, Laila Muderspach, Richard Paulson, Subir Roy, 2010, Page 275 ; Textbook of Obstetrics By D.C.Dutta, 5th Edition, Page 197