Pathology question in USMLE

[sohag100]

A 27 year old woman presents to her physician complaining of abnormal vaginal bleeding. She gave birth to her second child 8 weeks ago through uncomplicated vaginal delivery. On examination, the uterus is enlarged. Her lab tests show marked increased HCG. Her chest x-ray shows multiple nodules on both lungs. Her physician performs endometrial curettage.
What does the endometrial biopsy most likely show in this case?
A- Endometrial hyperplasia
B- Endometrial adenocarcinoma
C- Proliferation of cytotrophoblasts and syncytiotrophoblasts
D- Bundles of elongated spindle-shaped cells with prominent nuclei
Answer: http://medical-usmle.com/?p=1110