A 30-year-old woman who is eight months pregnant presents to the emergency department complaining of the sudden onset of feeling like she can’t catch her breath and sharp, right- sided pleuritic chest pain. She denies fever, cough, chest trauma or similar symptoms in the past. She is afebrile with a heart rate of 120, blood pressure of 110/70, respiratory rate of 24 and a room air oxygen saturation of 100%. Her lungs are clear, her heart sounds are normal, and she has mild bilateral peripheral pitting edema. Her chest x-ray is normal. According to the 2013 ACOG position statement, which of the following is the best test to order next? A) A bilateral lower extremity compression ultrasound. B) A blood gas on room air. C) A chest CT pulmonary angiogram. D) A D-dimer test.