A Person with Vitamin B Deficiency Often Exhibits a "Slow

A person with vitamin B deficiency often exhibits a "slow" nervous system. For example, their knee-jerk reflex is much slower than normal. Which of the following might explain why this is the case?

A) The neurons of people with vitamin B deficiency have more sodium channels in the plasma membranes of their neurons than normal.
B) People with a vitamin B deficiency produce less myelin than a normal person does.
C) Axons are slightly longer in a person with vitamin B deficiency, so the distance between transmitting and receiving cells is shorter.
D) People with vitamin B deficiencies produce weaker action potentials than normal people do.