You are answering a USMLE-style medical question. Question: A transvaginal ultrasound shows an intrauterine heteroechoic mass with numerous anechoic spaces and no identifiable fetus or amniotic fluid. Both the ovaries are enlarged and have multiple thin-walled, septated cysts with clear content. Which of the following is the most likely cause of the ovarian findings? Options: A) Chocolate cysts B) Corpus luteum cysts C) Yolk sac tumor D) Theca leutein cysts Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.