Your patient is an 18-year-old female who is alert and in moderate distress, complaining of abdominal pain and light-headedness. She describes a four-week history of worsening unilateral lower quadrant abdominal pain with onset of malaise, nausea and vomiting, this week.. Today, she is experiencing faintness and near-syncope with exertion. She denies pain or difficulty with urination. Her last menstrual period was two weeks ago. She is sexually active and uses oral contraceptives. Physical examination reveals marked tenderness and guarding with palpation of her abdomen. Her skin is cool and diaphoretic. HR = 121, BP = 90/58, RR = 18. The patient's presentation is most consistent with:

A) ectopic pregnancy.
B) pelvic inflammatory disease.
C) spontaneous abortion.
D) pyelonephritis.

A