A circle with centre $\mathrm{O}$ is shown in the figure. A rectangle PQRS of maximum possible area is inscribed in the circle. If the radius of the circle is $a$, then the area of the shaded portion is______________

(A) $\pi a^{2}-a^{2}$

(B) $\pi a^{2}-\sqrt{2} a^{2}$

(C) $\pi a^{2}-2 a^{2}$

(D) $\pi a^{2}-3 a^{2}$

A circle with centre $\mathrm{O}$ is shown in the figure. A rectangle PQRS of maximum possible area is inscribed in the circle. If the radius of the circle is $a$, then the area of the shaded portion is______________

(A) $\pi a^{2}-a^{2}$

(B) $\pi a^{2}-\sqrt{2} a^{2}$

(C) $\pi a^{2}-2 a^{2}$

(D) $\pi a^{2}-3 a^{2}$

127