Two polaroids are placed in the path of an unpolarized beam of intensity $I_0$ such that no light is emitted from the second polaroid. If a third polaroid,whose polarization axis makes an angle $\theta$ with the polarization axis of the first polaroid,is placed between these polaroids,then the intensity of light emerging from the last polaroid will be:

• A
  $\left( \frac{I_0}{8} \right) \sin^2(2\theta)$
• B
  $\left( \frac{I_0}{4} \right) \sin^2(2\theta)$
• C
  $\left( \frac{I_0}{2} \right) \sin^2(2\theta)$
• D
  $I_0 \cos^4(\theta)$