What is area of the shaded figure below?

• A. \[\frac{\pi }{\sqrt{3}}{{a}^{2}}\]
• B. \[\frac{\pi {{a}^{2}}}{16}\]
• C. \[\frac{\left( \pi -\sqrt{2} \right)}{4}{{a}^{2}}\]
• D. \[\frac{2\sqrt{3}}{\pi }{{a}^{2}}\]