The answer is A) Interferon Beta. This patient is suffering from multiple sclerosis. Her presenting symptoms of multiple CNS lesions and history of prior attacks should make multiple sclerosis high on your differential. The MRI findings of areas of demyelination (or plaques) confirms the diagnosis. Although IVIG and plasma exchange are used in Acute Inflammatory Demyelinating Syndrome and Myasthenia Gravis, they are not used in multiple sclerosis. Interferon Beta is often the first line medication used. Chemotherapy is a distractor.

Publication reference : Defining the clinical course of multiple sclerosis
Reference URL: https://www.ncbi.nlm.nih.gov/pubmed/25732366