The answer is B) Acute Inflammatory Demyelinating Syndrome, otherwise known as Guillain-Barre syndrome. Rapid onset of muscle weakness is caused by the immune system attacking the myelin sheath of peripheral neurons. The cause is often related to Campylobacter Jujuni which can present as initial gastroenteritis. Other causes can include Epstein-Barr virus, influenza viruses, and mycoplasma pneumonia. The disease is a demyelinating polyneuropathy and leads to weakness, often paralysis, and absent reflexes. It often effects the lower extremities first but can rapidly spread and lead to death, especially if the respiratory muscles are paralyzed. Thus patients must be carefully observed and some may require intubation. Brown Sequard Syndrome leads to a unilateral motor loss and a unique pattern of sensory loss not present in this case. Plasma exchange is not a treatment of multiple sclerosis. Transverse myelitis is inflammation of the spinal cord and often effect sensory, motor, and autonomic nerves. Like Acute Inflammatory Demyelinating Syndrome it can also be caused by infection of various viruses and bacteria, although Acute Inflammatory Demyelinating Syndrome's primary presentation is motor symptoms and is not a localized as Transverse Myelitis.

Publication reference : Chronic inflammatory demyelinating polyradiculoneuropathy: from pathology to phenotype
Reference URL: https://www.ncbi.nlm.nih.gov/pubmed/25677463