This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Female Genital Tract, Subject name: Pathology
A 22-year-old woman presents to the emergency room with a 2-hour history of acute abdominal pain and vaginal bleeding. Her vital signs are normal. Physical examination reveals blood oozing from the vaginal opening. Laparotomy shows an enlarged right fallopian tube with hemorrhage and rupture. What is the most likely cause of hemorrhage in this patient? 
Select and explain. 
A. Choriocarcinoma, B. Ectopic pregnancy, C. Infarcted tubal polyp, D. Intramural leiomyoma
B: Ectopic pregnancy
Answer: B: Ectopic pregnancy 
Explanation: Over 95% of ectopic pregnancies occur in the fallopian tube. Ectopic pregnancy results when the passage of the conceptus along the fallopian tube is impeded, for example, by mucosal adhesions or abnormal tubal motility secondary to inflammatory disease or endometriosis. The trophoblast readily penetrates the mucosa and tubal wall. The thin tubal wall usually ruptures by the 12th week of gestation. Tubal rupture is life threatening because it can result in rapid exsanguination. The other choices are rare.Diagnosis: Ectopic pregnancy