You are answering a USMLE-style medical question. Question: A 16-year-old girl is brought to the emergency department with constant abdominal pain over the past 8 hours. The pain is in her right lower quadrant (RLQ), which is also where it began. She has had no nausea or vomiting despite eating a snack 2 hours ago. She had a similar episode last month which resolved on its own. Her menstrual cycles are 28–30 days apart with 3–5 days of vaginal bleeding. Her last menses ended 9 days ago. Her blood pressure is 125/75 mm Hg, the pulse is 78/min, the respirations are 15/min, and the temperature is 37.2°C (99.0°F). Abdominal examination shows moderate pain on direct pressure over the RLQ which decreases with the release of pressure. The remainder of the physical examination shows no abnormalities. Laboratory studies show: Hemoglobin 12.5 mg/dL Leukocyte count 6000/mm3 Segmented neutrophils 55% Lymphocytes 39% Platelet count 260,000/mm3 Serum C-reactive protein 5 mg/L (N < 8 mg/L) Urine RBC 1-2 phf WBC None Which of the following is the most appropriate next step in management? Options: A) Methotrexate B) Nitrofurantoin C) Reassurance D) Referral for surgery Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.