The bob of a simple pendulum of length $L$ has a mass $m$ and charge $q$. The pendulum is suspended between the plates of a charged parallel plate capacitor. The direction of the electric field is shown in the figure. The period of oscillations of the simple pendulum is (acceleration due to gravity $g > qE/m$):

• A
  $2 \pi \sqrt{\frac{L}{g}}$
• B
  $2 \pi \left[ \frac{L}{\frac{qE}{m} - g} \right]^{\frac{1}{2}}$
• C
  $2 \pi \left[ \frac{L}{g - \frac{qE}{m}} \right]^{\frac{1}{2}}$
• D
  $2 \pi \left[ \frac{L}{g + \frac{qE}{m}} \right]^{\frac{1}{2}}$