21-year-old woman presents to the emergency depament complaining of pelvic pain, a yellow-green vaginal discharge, and fever, all of which have been worsening over the last 24 hours. She has no frequency or dysuria. She has no medical problems. Her past surgical history is significant for a cesarean delivery 2 years ago performed for a nonreassuring fetal hea rate tracing. She takes no medications and is allergic to sulfa drugs. She is sexually active with multiple male paners who sometimes use condoms. She works as a medical assistant. Her temperature is 38.2 Deg C (100.7 F), blood pressure is 100/60 mm Hg, pulse is 110/minute, and respirations are 12/minute. Her abdominal examination is significant for diffuse tenderness, rebound, and guarding. Speculum examination demonstrates a copious greenish vaginal discharge that appears to be coming from the cervix. Pelvic examination is significant for cervical motion tenderness and adnexal tenderness. Laboratory evaluation shows: Urine hCG: negative Urinalysis: negative Leukocytes: 15,000/mm3 Hematocrit: 39% Platelets: 200,000/mm3 Which of the following is the most likely diagnosis?