A23-year-old g1p0 woman presents with cramping, vaginal bleeding and right lower quadrant pain. her last normal menstrual period occurred seven weeks ago. on physical exam, vital signs are: blood pressure 110/74; pulse 82; respirations 18; and temperature 98.6°f (37°c). on abdominal exam, she has very mild right lower quadrant tenderness. on pelvic exam, she has scant old blood in the vagina and a normal appearing cervix. her uterus is normal size and slightly tender. on bimanual exam, there is no cervical motion tenderness, and she has slight tenderness in right lower quadrant. quantitative beta-hcg is 2500 miu/ml; progesterone 6.2 ng/ml; hematocrit 34%. the transvaginal ultrasound shows an empty uterus with endometrial thickening, a mass in the right ovary measuring 3 x 2 cm and a small amount of free fluid in the pelvis. which of the following is the most appropriate next step in the management of this patient?
a. methotrexate.
b. antibiotics.
c. observation.
d. dilation and curettage.
e. culdocentesis.