An air-filled parallel plate capacitor has a uniform electric field $E$ in the space between the plates. If the distance between the plates is $d$ and the area of each plate is $A$,the energy stored in the capacitor is ($\epsilon_{0} =$ permittivity of free space).

• A
  $\frac{1}{2} \epsilon_{0} E^{2} Ad$
• B
  $E^{2} \frac{Ad}{\epsilon_{0}}$
• C
  $\frac{1}{2} \epsilon_{0} E^{2}$
• D
  $\epsilon_{0} E Ad$