Why Is Losing Myelin in Multiple Sclerosis So Devastating

Why is losing myelin in multiple sclerosis so devastating?

A) A lack of sodium channels in the spaces previously occupied by the myelin halts action potentials.
B) The loss of myelin causes action potentials to move slower than they should.
C) The loss of myelin allows too much sodium to enter, overwhelming the sodium-potassium pump.
D) The loss of myelin allows too much potassium to enter, overwhelming the sodium-potassium pump.