<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 63-year-old woman presents to her primary-care doctor for a 2-month history of vision changes, specifically citing the gradual onset of double vision. Her double vision is present all the time and does not get better or worse throughout the day. She has also noticed that she has a hard time keeping her right eye open, and her right eyelid looks droopy in the mirror. Physical exam findings during primary gaze are shown in the photo. Her right pupil is 6 mm and poorly reactive to light. The rest of her neurologic exam is unremarkable. Laboratory studies show an Hb A1c of 5.0. Which of the following is the next best test for this patient?? A: CT head non-contrast, B: Direct fundoscopy, C: Intraocular pressures, D: MR angiography of the head, E: Temporal artery biopsy,  <response>: This is a clinical case scenario involving a 63-year-old woman with gradual onset double vision, difficulty keeping her right eye open, and a droopy right eyelid. She has a dilated, poorly reactive right pupil on exam. The question asks about the next best diagnostic test for this patient.Based on the history and physical exam findings, this patient has signs and symptoms concerning for a right third nerve palsy, including ptosis, mydriasis, and impaired adduction of the right eye. The differential diagnosis includes microvascular ischemia, aneurysm, mass lesion, and giant cell arteritis. Imaging of the brain and orbit is needed to evaluate for structural lesions. MRA of the head is the best initial test to assess for aneurysm or vascular disease. Temporal artery biopsy would be indicated if giant cell arteritis is suspected clinically. The other options listed do not directly evaluate the likely anatomical location of the lesion.D: MR angiography of the head 