A 26-Year-Old Woman Is Brought to the Emergency Department Because

A 26-year-old woman is brought to the emergency department because of a history of lower abdominal pain and vaginal bleeding which started yesterday. Her last menstrual period was 7 weeks ago and she started to have vaginal spotting a few days ago but has had slightly increased bleeding since morning. A urine pregnancy test is positive. A pelvic ultrasound shows a normal appearing uterus with an empty intrauterine cavity and a minimal amount of free pelvic fluid. Which of the following is the most likely underlying cause of this patient's presentation?

A) Abnormal ovum fertilization by 2 sperm
B) Benign proliferation of the uterine myometrium
C) Endometrial tissue development within the ovary
D) Implantation of a fertilized embryo in the fallopian tube
E) Torsion of an ovarian mass containing ectoderm, endoderm, and mesoderm