Of the following given choices;
A. a lack of electrolytes in the brain
B. fatty mitochondria
C. two nuclei in some neurons
D. progressive deterioration of the myelin
The answer is D.
Musciplte sclerosis is an autoimmune condition in which the immune system of the subject attacks the nervous system. Specifically, the immune system attacks the myelin sheath of neurons as though they are foreign hence causing them damage. Myelin sheath protects the neurons and also allows impulses to pass along the axon much quicker than it would be without the sheath.