<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 38-year-old woman comes to the physician for a follow-up examination. Two years ago, she was diagnosed with multiple sclerosis. Three weeks ago, she was admitted and treated for right lower leg weakness with high-dose methylprednisone for 5 days. She has had 4 exacerbations over the past 6 months. Current medications include interferon beta and a multivitamin. Her temperature is 37C 98.6F, pulse is 90min, and blood pressure is 11674 mm Hg. Examination shows pallor of the right optic disk. Neurologic examination shows no focal findings. She is anxious about the number of exacerbations and repeated hospitalizations. She is counseled about the second-line treatment options available to her. She consents to treatment with natalizumab. However, she has read online about its adverse effects and is concerned. This patient is at increased risk for which of the following complications?? A: Syndrome of inappropriate antidiuretic hormone, B: Progressive multifocal leukoencephalopathy, C: Parkinsonism, D: Tuberculosis, E: Aplastic anemia,  <response>: This is a multiple sclerosis patient case with a history of exacerbations despite interferon beta treatment. She is now being started on natalizumab. The stem asks about potential adverse effects she is at risk for with this new treatment. The key facts are:- 38-year-old woman with multiple sclerosis - Multiple exacerbations in past 6 months despite interferon beta - Now starting natalizumab- Question asks about potential adverse effects of natalizumabNatalizumab is associated with an increased risk of progressive multifocal leukoencephalopathy PML, an opportunistic CNS infection caused by the JC virus. This is the most concerning potential adverse effect of natalizumab. The other answer choices do not reflect known adverse effects of natalizumab.B: Progressive multifocal leukoencephalopathy 