Energy per unit volume for a capacitor having area $A$ and separation $d$ kept at potential difference $V$ is given by

• A
  $\frac{1}{2} \varepsilon_{0} \frac{V^{2}}{d^{2}}$
• B
  $\frac{1}{2 \varepsilon_{0}} \frac{V^{2}}{d^{2}}$
• C
  $\frac{1}{2} C V^{2}$
• D
  $\frac{Q^{2}}{2 C}$