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
A young woman with six weeks amenorrhea presents with mass abdomen. USG shows empty uterus. Diagnosis is: 
Select and explain. 
A. Ovarian cyst, B. Ectopic pregnancy, C. Complete aboion, D. None of the above
B: Ectopic pregnancy
Answer: B: Ectopic pregnancy 
Explanation: Young woman with six weeks of amenorrhea and mass in the abdomen and USG finding of empty uterus give the diagnosis of ectopic pregnancy. Ref: Textbook of Obstetrics By D.C.Dutta, 5th Edition, Page 198 ; 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