What is the energy stored in such a cell membrane if the potential difference across it is 7.05×10−2 v?

Capacitance 
C= e A/d 
or C=Q/V 
Energy stored in the capacitor 
W=0.5CV^2 

This a straight forward problem 
W=0.5 e A/d (V^2) 
W=0.5 x 4.5 x 4.75 x 10^-9 m^2 / 8.5 x 10^-9
m= 
W=... 

since d is the thickness and the energy is inversely proportional to energy stored in the capasitor then with the increase of the thickness of the membrane the energy will decrease.

C) reflection (i also looked up the other choices just to make sure)