A 23-year-old patient， amenorrheic for 16 weeks， had vaginal spotting， accompanied by nervousness， palpitations， and sweating.On examination， her BP is 160/110， HR is 110 BPM， and she is afebrile. She was found to have a uterus enlarged to 20 weeks' size and no fetal heart tunes audible with the Doppler. Lab test showed human chorionic gonadotropin (hCG) serum level approximatel