Nernnst equation related to equilibrium potential does not depend upon?

Nernnst equation related to equilibrium
potential does not depend upon?
a) Concentration gradient
b) Electric gradient
c) Non-ionic solution
d) Concentration of ions in two solution
Correct Answer - C
Ans. C. Non-ionic solution
[Ref Guyton 12th/e p.50; Principles of medical physiology p. 8]
Nernst equation is for ionic solution